I dont think so. All you need is to sign in your email n maybe about some personal information, but i dont think they will ask that.
Do you mean as a job / way to earn your living, or just as a hobby / to help scanlation teams? In the first case you probably need a diploma, and in the second you need nothing, you can translate even if you're not in any team
It’s all illegal anyways so you’re free to do what you want... although ppl usually like you to have good language and editing skills so the final product looks better. But if a scan group already said that they’re going to do a project or are working on it, they often don’t like other ppl working on it at the same time. Or you could apply to join a group and help them
Do you need a special permission to become a translator?