Can you turn into a demon?

Another answer from our community:

You can't. Demons are completely separate entities. God made the angels, the demons are fallen angels, and therefore, unless God himself decides to turn you into a Demon (not impossible, but I can rest fairly certain that its not even remotely likely), there is no way. You might be able to be possessed or even act as some sort of symbiotic host to a demonic entity, but you would never become a demon yourself.

You certainly can't. Demons do not exist. It's OK to believe in superstition, demons and so on, as long as you remember that this is all just about imagination, not anything real.