The WIF is converted back to hex by decoding using base58 and then truncated to fit 256 bytes. Afterwards, the mnemonic is generated by following the BIP39 standards. This can be done manually but it is hardly recommended because there is no good purpose of doing so.
No. None of the wallets are designed to function in this manner.

There is no point reusing the entropy from your vanity address to generate a BIP39 mnemonic. Mnemonic should be using their own unique entropy and the relevant standards. It is far better for you to just use the vanity address and the seeds separately instead of mixing them. This just complicates things unnecessarily without any real benefits.

Bluetooth has terrible latency and bandwidth and is generally not suitable for a deployment for a mesh network of sorts (ie. Bitcoin Nodes).

You must be thinking of Blockstream which has the participants operating with a satellite dish connected to the satellite. This can be achieved with something like Starlink, which has fairly reasonable latency and bandwidth. HAM radio is possible as well but you would run into some problems with potential obstructions and interference.

Yes.
Not necessarily. Older version of Bitcoin Core (Years ago) requires a backup every 100 transactions because the hidden keypool that is in the wallet.dat is that size. However, newer versions of Bitcoin Core are Hierarchical Deterministic or HD wallets for short. This means that there is a seed that can be used to generate as many addresses as you want without the need for multiple backups.

So long as your wallet is created in a hierarchical deterministic format, you do not need to create additional backups, granted that the passphrase to the wallet.dat is not changed after the backup.
This is dependent on what sort of wallet you're using. Most wallets uses a specific format that can easily be replicated. This ensures that the addresses are still recoverable in the event that the site is inaccessible for whatever reason.

This has the same concept as a Bitcoin Core operating in HD-mode. If you prefer a mnemonic instead of a wallet.dat, you can choose to use Electrum instead.

You generally shouldn't dump your private key if you don't know exactly what you're doing. All you need for a backup is your wallet.dat, assuming that you're using it with the later versions (then one would suffice). Individually extracting private keys poses unnecessary risks when all that you'll need is just the wallet.dat.
Yes, you can also specify additional flags like rescanblockchain 730007 731007 and that scans the blockheight in the range. But that shouldn't be necessary, is your wallet synchronized?
I'm not sure why is that necessary.

If you want, you can choose coin control within Bitcoin Core and spend the funds back into address A.

The other address should be your change address. Wallet usually generate a new change address on every transaction and they are usually hidden from sight.

Bitcoin Core should still display the correct balance.

Your ISP as well. Your ISP will know that you're establishing a connection to the pool and by association you're mining for the pool.

In addition, whoever is peeping into your traffic (if you're using a VPN, then the VPN operator) or any adversary will be able to see the traffic in plaintext if you're using stratum+TCP. Stratum+ssl will only reveal the connection destination (slushpool, etc).

I was referring to third-party payment processors, CoinPayments, etc. Perhaps could've said with better clarity.

I think it will work, with a fancier UI as well. Though I'd probably be more inclined to just code something like that myself, don't think OP wants a complicated plugin anyways.

Set up a HD wallet, make a donation script on your website.

For every query of the donation, ask your server to increase the index by 1 then display the address on the page. This way, every of your address is unique and there it is more convenient to store your keys offsite. I won't endorse any plugins for this, though I know wordpress has a few handy plugins but I've never tested them. Any payment gateway is out of the question, especially when anonymity is concerned.

Hmm, I don't think that is the case, or at least during my time mining at nicehash. My hashrate has always been roughly consistent but the payrate is the only one that fluctuates wildly, which is dependent on who rents your equipment.

Your accepted rate (in hashrate, not profitability) is determined by the shares you're submitting[1].

[1] https://www.nicehash.com/support/mining-help/mining-advanced-topics/is-it-normal-that-the-speed-jumps-up-and-down

Nicehash calculates the accepted rate by taking the rate of shares submitted and the difficulty of those shares.

So long as your stale is reasonable and the average speed after >24hrs is around 100TH/s then it should be fine. Your primary reference should be with your miner's stats.

The reason why the QR codes doesn't work across different wallet is because Electrum encodes the PSBTs in Base34. If you need to sign them, then encode them back into the original format.

I don't really recommend old phones as cold storage because it is quite well known that most wallet developers don't really care about mobile wallets. Some of them are littered with bugs and vulnerabilities. I'd very much rather just get a dedicated device (ie. RPi or an old laptop) if you want an air-gapped non-HW wallet. IIRC, I was able to extract the MPK out of a rooted phone quite sometime ago. Not sure if it has been patched yet.

If you don't include that in your businesses' TOS, then you're just plain dumb. The terms of service of almost any service out there requires the user to agree to this clause so that in the event that something happens, they have the rights to do something legally. Having that broad statement is a necessity if you don't want to face an expensive lawsuit (ie. having the user using their account in a way that harms your business but the narrow TOS doesn't give you the rights to stop it).

I think then selfish mining also plays a part. In certain scenarios, intentionally delaying the propagation of a block would make it more profitable than to broadcast it immediately. There are specific conditions for it to happen though, but generally the trend makes it kind of feasible.

I don't think most exchanges or services actually enforce 6 confirmations, for which the threshold hashrate is 51%. Else, you can get away with a lot less than 51%.

What issues do you have to connect to your peers if only your port 80 is open? You should still be able to establish outgoing connections unless something is actively blocking connections to your peers.

If you want peers to connect to you, then you can specify a non-standard port without any webservers.

If you've got the transactions, then does the balance tally with the transactions that are displayed?

Before you upgraded, was the wallet fully synchronized to the current date and time? If it was, then you can try to use your backup instead, though I'm more inclined to think that the balance that you saw might've been outdated.

Are there any transactions in the transaction tab? Is your wallet fully synchronized?

If there is a possibility of a total and irrecoverable loss of your backups, then you probably didn't ensure that there is sufficient redundancy. You should store them at different geographical locations and there are numerous ways of protecting them against everyday elements. That is not a good excuse to argue that digital backups are not suitable.

If you were to live in a totalitarian government, then you probably would have better things to worry about. There are ways to hide your data via stenography anyways.

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Of course, there are merits to both mnemonics and a wallet file. The answer to your question is that, you can. I would rather use a known standard, BIP38 to do so. However, if you plan on memorizing your seed, then I would urge you to think twice. You are far more likely to straight up forget your seed, either by human nature or through amnesia, alzheimer's disease, etc.

It is unfair to compare classical computers to quantum computers because they are fundamentally different. Reason why Quantum Computers are better at breaking ECDSA or other public-key cryptography is due to Shor's algorithm which can provide an exponential speedup, as compared to the quadratic speed up of classical computers. The qubits required to actually run Grover's with a pre-image would be fairly high, presumably (3+ times) far higher than Shor's just to outpace ASICs alone. That would mean that when QCs actually outpace the ASICs that we have today, then QC would be so mature that ECDSA would've been cracked more than a few decades ago.

I remember reading another research paper on this issue and the conclusion was that this isn't really a problem at all. [1]

[1] https://arxiv.org/pdf/1710.10377.pdf

No. QC remains too expensive for most tasks and the task for which it excels at requires specific algorithm, Grover's and Shor's for example. You can possibly do the operations faster than classical computers, but it would be too difficulty for it to match ASIC in terms of speed and efficiency.

I'm not really sure why pre-image would necessarily benefit them in the context of mining. You still need a very specific inputs for the block to be valid; finding a pre-image to a block hash doesn't do anything unless it is also a valid block header.

The methodology that Bitnodes used to find and determine Bitcoin nodes is inaccurate. The crawler essentially asks the nodes for their version and waits for a response and then subsequently requests for the other peers as well. This doesn't provide an accurate representation of the network as a whole. In fact, there is no way to actually accurately determine the node size.