Bitcoin has always used an UTXO system, so yes, outputs and inputs are absolutely needed.
If bitcoin is to change to an account-based system a la Ethereum, it would require a hardfork, so yeah, not happening.

By constructing a Merkle path to the root node of the Merkle tree.
(The hyperlink has a very good explanation of how it works; in fact the whole book is a good introduction to the nitty-gritty of bitcoin)

Blocks are stored as a LevelDB database  on the harddrives of computers that run the bitcoin client (i.e nodes) in $DATADIR/blocks On computers running Windows 7 and later the full directory path is: C:\Users\YourUserName\Appdata\Roaming\Bitcoin\Blocks
"Transactions" aren't stored individually, but are validated in blocks and stored as blocks.
Unspent Transaction Outputs (UTXOs) which represent the "Bitcoins" that are valid and can be spent.
They are stored as a database in the $DATADIR/chainstate folder.

Miners do not have special power to "decide" which transaction is legitimate or not, instead node software determines that on its own following a set of established protocols
The protocols state that bitcoin is able to act as money eg it must not be able to spend more than it has (i.e Outputs CANNOT be greater than inputs -- except in Coinbase transactions), it must not have been spent elsewhere (i.e it must be included in the UTXO set and the output being referenced shouldn't be present in the blockchain), it must be "mature" (i.e the nLockTime must have elapsed), etc.

If miners create a block that contains at least one  invalid transaction -- coinbase or otherwise -- other nodes in the network will reject the block as invalid and the miner would have wasted his electricity used to create the block.

There are no security implications-- as far as I know -- of running a pruned node.
Pruned nodes are still as secure as archival nodes because they download and verify the whole blockchain first but they don't just keep it on disk. For pruned nodes to be affected there should be a blockchain reorg longer than ~3 days worth of blocks.

Pruned nodes still validate consensus rules too.

The only downsides are not related to security: not being able to serve historical blocks, not able to rescan the blockchain, etc.

If your node is not a pruned node (i.e archival node), then it serves historical blocks to new nodes on the network to help them bootstrap.
Which is why your upload bandwidth is high.

Not true.
Pruning deletes old blocks data after they've been validated, only a keeping the last few hundred blocks or so depending on the size specified.
So you do need to download the whole blockchain and verify it obviously, but you do not need to store them before you can prune; pruning happens on the fly.
People run full pruned nodes on raspberry Pi's with 64GB memory just fine.
This applies for unpruned nodes too.

Telegram wasn't banned in Russia because of the TON ICO, but rather because they wouldn't Give up decryption keys to the government.

Apparently the coin is just an asset on the waves platform. Try to create an online wallet and you'll see.
PS It's funny that their address is that of a UPS store.

Ethereum can't be considered a security in any way because it never had an ICO!
Ethereum Classic is the original blockchain that had the ICO, not Ethereum. Ethereum is a fork of Ethereum classic and forks can't be considered securities, so Ethereum is in the clear.

This is what Buffet said:

Which suggests he thinks bitcoin and other cryptocurrencies are Ponzi schemes which isn't true because they are actually used outside of speculation.
People get paid in cryptocurrencies, people buy items with cryptocurrencies.
Ironically, stocks themselves aren't used for anything else apart from speculation: when you buy stocks of a company you're hoping another person pays more for it. You can't buy items with stocks, you can't pay for services rendered in stocks.

So I guess investing in stocks is gambling too

Try to contact the so-called team member on another platform eg twitter or email. Sometimes fraud ICOs use people's names and faces without their consent or knowledge.

There's Waves, Stellar (XLM), Stratis, Byteball, Neo, etc.
But Ethereum fees are higher because it's the most popular.

If you have 2 accounts in bitcoin core, the default account and a new account named "A", and you have 2 BTC in default account but 5BTC in account B.
If you use the sendtoaddress command to send any amount of bitcoin, it will always debit the default account whether it has a balance or not.
For example if you send 3 BTC using the sendtoaddress command and the default account has 2 BTC balance, the transaction will succeed because Core will choose coins from the other account that has funds but still debit the default account so the new balance for the default account will be -1 BTC.

If instead you wish to send 3 BTC from the new wallet B instead then you'd use the command instead.
For example This time it will debit account B instead and the account balances will be: default address: 2BTC and account B: 2BTC

If you wish to adjust the balances of different accounts then use the command. This is a cosmetic change  within the wallet and so there's no need for a bitcoin transaction.

Should most likely be blockchain.info then but their mnemonic phrase doesnt encode private keys unlike in BIP39 or Electrum but the (wallet identifier &) password.
If you have that phrase then you can enter it here to get your wallet identifier & password.
With the email address or identifier and password you should be able to access your wallet.
They also stored a backup file containing the private keys in an aes.json file, do you remember ever using that?

You're doing nothing wrong; the darkserver.eu site is down for maintenance which is why it's throwing 404 error.

If wallet_1 gives you other addresses apart from then you have the wrong seed (either a word is wrong/different or the order is wrong)

It's impossible for a wallet to be watch only when you create it with a seed phrase so my guess is that you pasted the address instead in the first place.

Go to the console (menu -> console) then paste and see if it shows true or false.
If it shows false then you definitely have a wrong seed.

You don't need up to 145GB space if you prune.
You can go as low as 550MB.

By "account" do you mean accounts with different HD seed & different addresses, or do you mean other addresses in the wallet.
If it's the former then doesn't support accounts and will send from the default account ""

If it's the latter it just select UTXOs and spends according to the amount being sent.

There's a list here with the exchanges that support the coins.
So just paste your addresses there to check the amounts they have for each fork.
 Findmycoins.ninja has a longer list but some of the forks may be untrustworthy.

If you're going to download other wallets then first send out all your bitcoins, and install the wallet software in a virtual machine so it is sandboxed and any malware present cannot affect your host machine.
As long as the blockchain of the forked coin is alive you can always
"claim" your fork coins at a later date.
Once the snapshot is taken then you can spend your bitcoins and it would not affect your fork coins.

Transaction clustering algorithms render a lot of mixer services useless.
Bitcoin was not designed to be private; if people want  private transactions then they should use a fungible cryptocurrency

Here are options to try:
1) connect with a different browser entirely (eg Chrome)
2) Use another method apart from Metamask to unlock your wallet.
If you're going to enter your private key or seed into any website, download the MyEtherWallet website from here And and do everything from there, then copy the final signed transaction and paste it in the online website to broadcast it.