the majority of users have to go with whatever their wallet software decided for them. and unfortunately, it's not always obvious what exact derivation path is being used.
Yeah, I would echo what pooya87 has said above. If your wallet software is not clear which derivation path it is using, then you shouldn't be using that software, exactly because you will likely run in to problems trying to recover access to your coins on a different piece of software in the future. Stick to reputable open source wallet software and you will not run in to such problems.they need to write the derivation path down along with their seed phrase, might need another titanium plate to record that.
This should really only be necessary if you are using a really weird derivation path, which as I said above, the vast majority of users should never do. There are tools out there which will scan the most common alternative derivation paths automatically for you in order to try to recover your coins. Electrum itself offers this functionality for BIP39 seed phrases.so there must have not been anyone ever come here on the forum who said they put in their address and sent money to it but then found out they made a typo and the money is sitting there on the blockchain...the probability of that happening is too small to have ever happened. 
good to know.
Not as far as I know. Any time someone has sent money to the wrong address it has either been they copied the entirely wrong address or they were subjected to clipboard malware, and did not bother to double check before hitting send. good to know.