Yes it can. You can check this minting sc for an example https://egldhub.dev/post/elven-nft-minter-smart-contract-59 You will need to pass different params that you need in order to create the nft to a method from the sc

Not at the computer right now but most providers would accept a token (that you generate) and would return a signature after login. The message signed has the format “address+token+{}” (without the + sign). You can use that message, with the address and signature to verify it on your backend

Hi! Not sure about a guide but you can find some SC examples here https://github.com/ElrondDevGuild/awesome-elrond-dev-resources

It's no scam. It's an sft we want to distribute to our holders and they can "open" it and get a reward.