I am referring to the @ tag. I was told for businesses or people looking to sell something, this is ideal.

I am just having a hard time finding one on every platform to be the same. One or more are usually taken.

It is cleaner and makes it easier to find them. It is not necessary though. A lot of accounts have different tags for them because it is honestly very hard to do this these days. You could pay for it if it is an option but I don't think you need them all to match.

Make them similar enough. Don't worry about getting the exact user tag everywhere. There is a good chance you won't be able to. A lot of people will use words like "Official" or "real" in the titles to help too.

I would not worry too much about this. Usually when you put links to socials on other sites, you do so with clickable links anyways. Once people follow the account, it won't make much of a difference if the names match or not. Just make sure the title name matches and the bio-info is the same.

Matching doesn't really matter, it is more about reach.

It doesn't make a difference if someone's handle is the same on Instagram as it is on X or YouTube, so long as I am able to easily follow.

I don't think it matters if they are 100% the same, just make sure the actual name not the handle says the same thing. It isn't too difficult for people to find accounts across multiple platforms either if they really wish to follow them.