Okay, that came out wrong.
I meant no node can tell if its block (the block it has received) is not going to be orphaned in the future for a block with a higher POW.

If no one stores blocks where do nodes get blocks to bootstrap from?
Obviously for a node to receive a block from a peer, another node has to have stored it then sent it.
If you don't store it, you can't send it.

AFAIK, orphaned blocks are stored in the node's blockchain forever, iff it received it when it wasn't orphaned yet.
No node would upload a block that wasn't part of the canonical chain (ie a new node in the network won't receive old orphaned blocks)

This is an example of an anyone-can spend address: 3MbZjYS1Kjo5An9vVCwZYTd2JeobwjUsFh.
The redeemscript is which is The redeemscript of the address is the solution to the equation z + x = 7; x + y = 8; z + y = 9.

Let it synchronise then.
It shouldn't take time to download the block headers, depends on your internet connection, or the server you're connected to.
Either check your internet connection, or connect to a different server.

I don't think it'll be possible on Electrum since it uses one derivation path for each wallet.

PS Samourai mobile wallet on Android has the option to receive change to like addresses.

The closest thing to an LN wallet on an iPhone is the iMessage Zap widget]/url]

In case of a Blockchain reorganisation, perhaps.
There's no way to tell it's "no longer needed" though.
There's no central arbiter that decides whether a block is needed/valid or not.
Nodes take the longest chain with the highest cumulative POW as the canonical blockchain.
The canonical blockchain could change if nodes receive another block that follows consensus rules but has a higher difficulty than the one they possess, even though the probability of  a blockchain reorg 6 blocks deep is small, it's still theoretically possible.
For example the March 2013 reorg was ~21 blocks deep.

When a HD wallet syncs it generates a set of addresses from the derivation path m/k'/0/i, then it scans the blockchain for transactions related to those addresses. If there are transactions related to that address (even if the address is empty), it generates more addresses until the gap limit is reached.
The gap limit is a certain number of addresses in a row which have no transactions at all.

The default gap limit is 20.
Other wallets may have different implementations.

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Go to Menu -> Network -> Blockchain.
Is the number of verified blocks the same as the number of blocks on any block explorer?
It's currently 525,335 right now.

If you want to do it locally download the bitaddress website on your computer, go to wallet details, enter your private key, click, view details and it'll show you both compressed and uncompressed address.

Is this really possible?
Both formats use different schemes to calculate the checksum, is it possible for there to be anintersection between both?

If it's a 3 of 3 multisig, in order to import it into Electrum, you'd need all three xprivs (master private keys)
Go to file->New/Restore
Enter a name for your wallet
Select "multisig wallet"
Choose the multisig scheme (eg 2 of 2, 2 of 3, 3 of 3,)
Select "use a master key) if you have the xprivs or "use an existing seed" if you have the seed phrases
Enter the first xpriv, click next
Save the xpub , click next
enter the xpriv or seed of second cosigner, click next
repeat the procedure for the last cosigner
enter a password for the wallet for security, click next
And your multisig is restored.

^
Electrum seeds are not BIP 39, even though you can restore BIP 39 seeds on it.

Apps and QR codes work well enough already .
Just use your wallet app on your phone, scan the QR code and that's all.

I'll assume by pool You mean mempool which is where unconfirmed transactions are stored in nodes. There's no global mempool; all nodes have theirs.
And by "data" I assume you mean unconfirmed transactions.
There are other things concatenated with the previous block header hash before it is hashed to find the target: the version, the Merkle root of all the transactions in the block, the timestamp, target and nonce.
This is the template for the candidate block's block header hash. They hash this while iterating the nonce, then the timestamp until they find a hash that is lower than the target hash.
As explained above, it is the mempool and is peculiar to each node.
They verify it against the set of protocol rules. For example a transaction is not allowed to have more output than input (ie spend more than it has). If any transaction doesn't follow the rule then it's invalid and is discarded by the node and not related further in the network. If a node keeps relaying invalid transactions to another node then the recipient node will ban that node for some time.
I don't see how the mempool can be compromised but like I said above, if you send invalid transaction or block to the node it will discard it and won't relay it so it doesn't propagate in the network.
Finding the right nonce is the job for the miners as they are the only ones allowed to append blocks to extend the blockchain, so the process must not be trivial.
For a miner to be able to extend the blockchain with his block then he must have expended some costs (usually in the form of electricity) and so is incentivized to follow the rules.
However, if he doesn't follow the rules and includes invalid transactions (transactions that don't follow the protocol rules) in his block, then his block will be rejected by other nodes in the network and his work will be a waste.

Finding a nonce which hashes to less than a particular target is hard work because you have to try a whole lot of values but verifying that this nonce is valid is just one hash which doesn't take time or consume CPU resources at all.

It refers to BIP 39 which specifies a way to encode a private key in a mnemonic phrase.
Electrum uses a different encoding scheme so the two are not compatible.
Although Electrum's seed versioning system is superior, BIP39 is more popular.

Are you sure it's not from your node (or wallet)?
9 gwei gas price actually gets your transaction confirmed within 5 minutes.

No, they can be as short as 26 characters eg to as long as 34 for P2PKH addresses (addresses that start with '1')
P2SH (testnet) addresses can have up to 35 characters IIRC.
Bech32 segwit addresses can be as low as ~14 characters long eg to as long as 74 characters.
It depends on the encoding being used by the coin to generate addresses.

No, they have the same RANGE but they're not always the same length.
The encoding provides the range of values that generates a valid address.

In some cases however, the address lengths are always the same because of the way addresses are derived.
For example Ethereum addresses are always 40 characters long (plus the 0x prefix to give 42 chars) because it's the last 20 bytes of the SHA3 hash of the  public key controlling the address.

Wow, that's a lot!
I doubt you'll be able to find a tool that does that unless you make one yourself since a master private key -- like a seed phrase -- derives many addresses and is meant to be used for a single wallet.

By wallets do you mean different master private keys or different addresses?