Is it possible to change the first and last name if initially they were not real?

No, according to the rules of this, this cannot be done. There is only one exception, which is possible.

You can send Support Case with a request to change the name and (or) the name, if you really changed them. This will require an official document. Attach a scan of your new passport to the certificate scan. After that, your last name (or name) will be changed by support.

Support it really does. If you originally invented a first and last name, and you have nothing to confirm the fact of their replacement, you have only one way to make your account legal — register a new account in your last name and first name, and quit the old account. Officially, closing it still will not work, since you cannot confirm, that you own it.