It must be it, answers 3 & 4 'speaks for itself'.
If the bitcoin-equivalent amount is computed by their platform, then they are indeed miscalculating the deposit amount (in BTC).

Or have you been using the dollar input box in Electrum's 'send' tab instead of 'BTC' when sending to the casino?
Because every platform is using different APIs to get the market price, the fiat price will not be the same for all platforms.
If so, the selected source in Electrum's 'fiat' setting must have a different market price than the one used by Tigergaming.

This shouldn't be an issue since Electrum will not deduct the fee from the output's amount, except if you've replaced it via rbf ("increase fee" option) and selected the option to do so.

In that case, check the transactions in your Electrum's history tab (Right-click->View Transaction).
And see if the output (your poker site deposit address) has the same amount as what they've credited you.

If not the same, then they are either lying about the amount being deposited or there's an issue with their site.
If it's the same, then there's "something" wrong with your Electrum or setting (but definitely not a hack since the funds would've been wiped if so).

If that happens, you don't have to restore the watch-only wallet, the saved "local transaction" can be removed by the right-click menu "remove".

That sometimes happen if the server you're connected to somehow dropped it from their mempool,
or since you're using a cold-storage set-up, you may have clicked "save" instead of broadcast after loading the signed transaction.
Either way, it will be saved as a 'local transaction', indicated by the 'blue computer' icon instead of the 'check', 'pie' or 'clock' icon.
Example:

There may be issues with the latest header(s) that you've received and for some reason, Bitcoin Core may have invalidated it.
Try to check your logs for error lines about "block headers".

Log file is in the 'data directory' named "debug.log".

Yes, only if you're referring to the "root key" in your paper backup.
Armory is a "Hierarchical Deterministic" wallet which means that every private keys and addresses that it will generate can be recreated by the root key.

Otherwise, a single exported private key can only restore an address; one private key can only restore its address pair, not the whole wallet.

IDK if there's a way to get a 'master private key' from the 'root key' to be able to create a "versatile backup" but the instructions in the reply above you should be sufficient in case you need to export to another client.

While the GitHub repository and site use the trustworthy "bitcoinjs-lib.js" and the hashes checks out,
it's still using an outdated version 3.3.2 which might contain bugs that were fixed within that 4-year gap.

Anyways, why don't you just create a paper wallet using Bitcoin Core, Electrum or other trusted clients?
You just have to export the private key of the address that you picked.
It's basically the same except for the fancy wallet layout that you can print.

That's almost 2 weeks already, it's not a good sign.
Considering their reviews in various "trust" sites (refer to post #10), I wouldn't be surprised if they do not credit your deposit.

Which board? Here at Beginners and Help?
If yes, those old topic at the top are "pinned" (indicated by the pin icon near the author: ).
Those are pinned because a moderator deemed it useful for those who might visit this board, specifically for beginners.

If its for the other boards, please specify.

'SHA256SUMS.asc' contains signatures which you can use to verify the file 'SHA256SUMS' which contains the SHA256 hashes of the Bitcoin Core binaries.

There are instructions in bitcoincore.org download page: Verify your download

The way it's described in their support page is: temporary in a way that it's only used in the session(s) when it's used.

After restarting the device, the accounts that you've used in the session will be removed from your Ledger Nano like they never existed.
But it can be accessed again by starting another session by typing the exact same temporary passphrase again.

It can be used for long term since you can reproduce the created "temporary wallet" in the session by using the same seed phrase (recovery phrase) plus the temporary passphrase.
Like I've said, it's like a "hidden wallet".

Adding passphrase (BIP39 passphrase) to a BIP39 seed phrase will produce a different binary seed, thus different set of keys.

So, by using a temporary passphrase, you'll have access to a different wallet that can only be accessed by typing the temporary passphrase.
Think of it as a separate "hidden wallet" in your Ledger Nano.

There is one widely used scheme but it's not using a fake transaction (can be used in that "every day spending" scenario).
It's done by utilizing "replace-by-fee" flag which makes a transaction replaceable as long as it's not included in the blockchain yet (0 confirmation).
However, such transactions can be easily identified so merchants that accept 0-confirmation txns (eg. some Casinos) don't grant the "instant deposit" benefit if it has an 'rbf' flag.

It goes like this: The transmitted "unconfirmed" rbf flagged transaction will be seen by most clients and the victim,
but when the scammer received what he paid for and wants to "cancel" it, he just have to send another transaction transaction that spends the same input(s) and replace the output with his own address. That essentially boots out the old transaction from most mempools.
Bitcoin Core with default setting are setup to replace the older transaction with rbf flag as long as the new transaction follow some specific rules.

BIP-0125: https://github.com/bitcoin/bips/blob/master/bip-0125.mediawiki#Implementation_Details

The default installation and data directory has always been the same since 2014, except if you've used the "portable version" or set a custom datadir.

With that; if you didn't wiped the disk, the OS is intact and you're able to boot it:
you can install the latest version of Electrum and it should be able to find and open the wallet files without issues if it's still there (but don't).
Electrum will automatically search for the last opened wallet file logged in the config file in Electrum's data directory, clicking "next" will upgrade that wallet file but it might encounter issues during that process.
So it's best to find the wallet file first to be able to create a backup in case it happen.

At least create an offline backup of your "Recovery Phrase" from 'Security' settings. (write it on a paper and store it in a safe place)
That way, even if you (will) encounter issues with Blockchain wallet, you can import it to another client and access your funds through it.

Last time I tried to create a new wallet, they didn't prompted me to create a backup.

'Next' in Electrum is grayed-out because you've pasted an invalid private key in there.
Probably what hosseinimr93 has pointed-out or there's still spaces.

Another possible issue is, you might have selected the wrong option when creating a new 'imported' Electrum wallet.
You have to select "Import bitcoin addresses or private keys" instead of standard wallet.

Electrum's wallet file doesn't have a strict naming system, it can be named anything and it doesn't have an extension like ".dat"
The default names are "default_wallet" for the first, "wallet_1" for the next, then "wallet_2" and so forth (if you didn't changed the wallet name).
But if it's from a very old version, look for "electrum.dat" file.

If that's the case, you can try Electrum versions lower than 4.x for the watch-only wallet on your Laptop.

But you'll be stuck with those old versions so I'd also recommend you to use Electrum on your Cold-storage Android to be able to use the latest version.
Electrum supports camera and QR codes in both desktop and Android so transferring the transactions for signing will be easy.

I don't know if Airgap Vault supports PSBT (Partially Signed Bitcoin Transaction) which Electrum generate when exporting unsigned transactions;
if it doesn't, the whole setup wont work.

neutraLTC just logged-in today: https://bitcointalk.org/index.php?action=profile;u=181180.

Take note that the user will be notified via email when you sent him a PM, unless he disabled it.

You can try to contact the same miner (mining pool) who mined the transaction (page8) if he'll agree to your offer.

Blockcypher accepts such transaction but the majority of the nodes and specially miners will just reject that transaction.