Nobody forces you to help them, if you want you are free to help only those who help you, what is the problem?

I agree, I don't see why people should be forced to help.

I'm sorry but I have no way to limit these accounts and anyway I wouldn't do it without proof.

Blocking another user's post has been around for a while but was dropped because some were blocking posts from moderators.

the profile should be able to be deleted but the answers should remain in the profiles of those who answered.

You can't prevent someone from erasing their personal data. We must therefore give the possibility somewhere, perhaps by making a request to a moderator and explain this possibility in the FAQ.

@Czar, yes it would be perfect, thanks

@Librarian, this rule doesn't work for the old requests, currently only a moderator can validate your answers, I do it every now and then when I think about it.

...and if someone thinks the answer is wrong he/she can either say so in the comments or suggest the correct answer.

This button existed before, but it was removed because many used it to upset whoever answered and not because they thought the answer was wrong.