I'm curious, do you still have a link to that old version cold-storage issue?
It's better if everyone can read and analyse that issue so people here can give you more accurate answers.

For now, if it's not an Electrum Bug, then there will be no problem even if you have a different version of Electrum as long as all of your wallet's addresses are legacy '1'.
Lastly, the most relevant old offline signing-related bug that I've heard was: 2951: Cannot sign transactions while offline - for versions < 2.7.9

There was an old discussion about this and the OP tried all the previous ways to get the wallet.aes.json file but none of them worked.
That's after the 2017 upgrade.

Here's the Topic link: Obtaining blockchain.info wallet.aes.json - process changed?

AFAIK it's disabled by default but the config that I'm using is still the same as the old builds that I've tinkered with the settings so it could be wrong.
Anyways, it's not a newbie-friendly way to send bitcoins so it must be disabled.

That will only show directly of you enabled it in the settings (Tools->Preferences->'Transactions' tab->Advanced preview).


Otherwise, it will only show a fee-slider, 'advanced' button (same as preview) and 'send' button.

That looks like a part of the 'DNS Seed' that Core uses to "jump-start" the connection to the network.
The purpose must be to minimize the risk of new nodes connecting to those node instead of the proper ones, but that's quite a small list compared to an active node's own banlist.dat.

As I've said above, your node have its own "banlist" and will automatically ban the IP of misbehaving peers for 24hrs (default) if it detected a malicious activity.

Your questions all over the forum are quite random... from mining, full nodes to private keys, all.
You're gonna love "Mastering Bitcoin" book if you still haven't read it.

Here are some resources that you should consider reading:

• Mastering Bitcoin: https://en.bitcoin.it/wiki/Mastering_Bitcoin (Download pdf/other format) - I can't recommend this enough, this explains Bitcoin from the very basic ELI5 concept to the most technical answers.
• Bitcoin Whitepaper by Satoshi Nakamoto (Some info were unimplemented but most are still relevant): https://bitcoin.org/en/bitcoin-paper (Select language to download)
• Bitcoin Core RPC: bitcoincore.org/en/doc/0.19.0/rpc (Select from the command list on the right) - Commands you can "play with"
• Developer Documentation (most are technical): https://bitcoin.org/en/developer-documentation - use the links and search function.

He's just nitpicking and explained that it's not actually 2 to the power of 256 but only until the highest valid private key to be exact.

2^256 = 115,792,089,237,316,195,423,570,985,008,687,907,853,269,984,665,640,564,039,457,584,007,913,129,639,936
isn't equal to 0xfffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364140,
in decimal = 115,792,089,237,316,195,423,570,985,008,687,907,852,837,564,279,074,904,382,605,163,141,518,161,494,336

Those aren't hash, 0-F character strings are Hexadecimal (HEX).
Most Hashing algorithms' outputs are just represented as HEX by most tools, that's why it looks the same.

Read the answers of the developers themselves, first and second upvoted posts: https://bitcoin.stackexchange.com/questions/9305/why-not-retarget-on-every-block
Specially the one from 'G. Maxwell'.

The answer is simple, the number of broadcast new unconfirmed transaction have no limit and may increase or decrease depending on the situation (but each node's mempool does have limits).
While the number of transactions that can fit in a block have a limitation and the number of blocks per day is also limited to an average of 1 block per 10 minutes.

Answered by jackg.

That depends on the difficulty (answer to #2). The higher the difficulty, the lower that "target" will be.
As the wiki said, it's a "256-bit number" which is a 64-characters (HEX) [64characters HEX = 32Bytes= 256-bit].
It's the same number of characters as a SHA-256 hash.

So the miner will try to create a "block header" with a SHA-256d hash lower than the target to win a block.
Read this: Block hashing algorithm.
If the hash isn't lower or equal to the target, then the miner will change the "nonce" that will change the hash.
If that new hash isn't lower or equal to the target, repeat the above until it does.

This depends entirely on the client, some badly-configured wallets deduct the fee from the amount to send by default.
But most clients will try to find a higher valued UTXO in order to send the full amount to the desired address.
Some are configurable to do what the user wants.

Since there are a bunch of corrupted data in your block files,
try to run Bitcoin Core with a fresh data directory containing a new copy of your old wallet.dat, then open core while offline.
Create a folder to any directory other than the default, then set that temporarily in a bitcoin.conf file inside '%appdata%\bitcoin' folder.

Example (Windows):

• Create a folder name "bitcoin_temp" to "D" drive.
• Paste the copy of your wallet.dat inside that folder.
• Open %appdata% (Win+R, type  %appdata%) then open Bitcoin folder.
• Create a bitcoin.conf file inside, new->text doc->rename including the extension from "New Text Document.txt" into "bitcoin.conf".
• Open it using a text editor and type datadir=D:\bitcoin_temp
• Disable your internet and open Bitcoin-qt, then do the dumpwallet command.

Change the data directory depending where you created the folder.

If the wallet turned out corrupted, start bitcoin-qt with --salvagewallet.

• Create a shortcut of bitcoin-qt, right-click the shortcut and select properties.
• In the "target" add <space>--salvagewallet at the end and apply/ok.
• it should look like this: "C:\Program Files\Bitcoin\bitcoin-qt.exe" --salvagewallet
• Then open Bitcoin Core using that shortcut.

This is what I noticed based from that bold phrase:
Either one of the two possible outputs doesn't have two recent incoming transactions so those aren't your Electrum BTC address.
The other one looks like an exchange change address.

• 1G3BdSyNiyLGtyEN84T2wcvaGDzaZfGG3i - Last TXs: 2020-04 and 2019-08, can't be this one
• 3JsffzphrK2GpRJcLixKyxn7HuF2xn8CqH  -   Last TXs: 2020-04, just one
• bc1quq29mutxkgxmjfdr7ayj3zd9ad0ld5mrhh89l2: Received a total of 429,660.48723108 BTC (you're a 'whale' perhaps)

So, it could be a different Bitcoin address, it was changed by something or Gemini is lying.

---

Edit for the new reply: 1G3BdSyNiyLGtyEN84T2wcvaGDzaZfGG3i only have one recent transaction, it can't be the same address that you've used to withdraw from Coinbase.

Just press "WindowsKey+R" to open 'Run', then type %appdata%, Enter. You'll be able to browse inside even if it's hidden.

BTW, last time I tried copying Electrum 3.3.8 wallet with legacy bitcoin address to Electron 4.0.12 datadir (about 4 months ago),
it didn't worked due to wallet version compatibility issue, newest version 4.0.14 wont work either.
However, a copy to ElectrumSV's datadir, worked.

I wouldn't call that drawback because "Trust" was already covered by Atomic swap, it's not a simple send and receive transactions.
You don't have to trust the other party because the trade wont proceed if there's hiccup or even if it's at the final stage, you can refund your coins.

Those addresses where you should send your funds are designed to have a timelock, refund/spend conditions and a "secret" (it's also created using your own keys);
those are configured to be recoverable in case of a failed trade & the "to-be-traded" coins can only be spent by both parties unless the secret was revealed to finalize the trade.

The fee wont always be an issue either, a 1input-2outputs tx @50+sat/byte is still a lot cheaper than any Exchange's withdrawal fee or Instant Exchanges' trading fee.

---

One potential drawback for the fee is: if the either one of the final transaction got stuck unconfirmed due to a really low fee, the occasional "mempool clogging",
and the timelock for the refund transaction was due, then the other party can broadcast that refund tx (if it's RBF) or send it to a 'friend' solo-miner/pool to double-spend the inputs of the unconfirmed claim transaction.

There's nothing "harsh" about that quote, it's actually mild and comforting  

FTR, There is currently no recorded collisions for both SHA-256 and RIPEMD-160, Bitcoin is using the two famously for computing "pubkey hash".

For the particular hash function, projects that are using it like Bitcoin would start looking for safer alternatives.
Like if SHA256 proved to become unsecured after discovering multiple collisions or successful collision attacks, developers might consider using SHA512 instead.

<addition, because my answer didn't really answered the question: For Bitcoin address collisions (because it was created through hashing),
the two persons who own the private keys that derived the same address can spend each other's funds>

No.

For "pubkey hash", Bitcoin has been using two entirely different hash functions. So if one got compromised, there's another one to break.
For some "Redeem script" and "P2SH addresses", the same as above.
For Mining, Bitcoin uses SHA-256d (d=double) for a reason: (wiki: SHA-256d)

Are those questions part of your exam?

Here are the "technicals": BIP: XX - Atomic Cross Chain Transfers | Re: Alt chains and atomic transfers

Most of those advertised "Decentralized Exchange" use something like that under that hood.
It's basically a bunch of scripts made from your own public keys that have certain conditions before each party can proceed & spend the final transaction's outputs.

That's also one of the disadvantages versus regular instant exchange because it's only compatible with coins that supports such scripts, the coin selections will be limited.
Another one (an advantage rather) is newbies normally mess-up handling their funds when it's in a non-custodial client like a decentralized exchange,
not really a disadvantage but it's a usual beginner's issue (Bec.: Beginners & Help).

Good thing that you've used you own deposit address to create that watch-only wallet.
So, what actually happened is that you have deposited your balance from Coinbase to Empire, Electrum didn't took part of that transaction.

The name clearly tells that it was created using "import bitcoin addresses or private keys" option then you pasted that address.

He will only need to backup once after he imported the keys or dumpwallet file.
After that, the 'new backup' can still generate the new/future addresses/keys as long as the hdseed is the same.
Old backups however wont contain the imported prv keys.

Better use dumpwallet on wallet1, then importwallet the dump file to wallet2.
That's doable within a minute if you're fast, minus the rescan.

You can only choose one of those software; or none, just create a bitcoin wallet (eg. Electrum) and join a Bitcoin mining pool.
Using the article in the post above, you can easily configure your miner to connect to a mining pool, then it's plug-and-play.

As long as your phone's browser supports full webpage view and connected to the same network as your Antminer, it will work (mini-browsers might not work).

Withdrawal and miner configuration will depend entirely on the pool of your choice, some have an internal account which requires you to withdraw or set an auto-withdrawal to your own wallet.
Some will automatically send your earned BTC (for a specific timeframe) to your bitcoin address.

You should post a reply to bitcoin mining pools' official threads for support because settings differ per pool (although it's already written in their respective OP).
Here are a couple of options: KanoPool | ckpool

There's no option "watch-only" in the new/restore wallet menu. Are you sure that you're using Electrum?
The two ways to create a watch-only wallet is to select "Standard->Use a master key->Paste a master public key" or "import Bitcoin addresses or private keys->Paste an address".
The difference will be the wallet type after the wallet name: [standard, watching only] and [imported, watching only], respectively.

Coinbase isn't really a wallet so you can't call it "non-watching", your receiving address still belongs to them.
They just crediting your account based form your deposits.

For the main question, you're "fucked" if you don't know where you got that address.
If you know where it came from, then you can investigate further.

You can follow BitCryptex's suggestion to remove it from your history.
If you do that, the funds from that transaction will return to your available balance because it wasn't "processed" in the first place.

To properly send a transaction, you need to directly click "send" after filling out the address, fee, amount, etc. (next version will be different)
If you have to use "preview", make sure that you will click "broadcast" after viewing the transaction's info.