Don't get me wrong, your opinion has been helpful for me and I appreciate it.
However, let me be a little bit more clear about this.
A)It's been said that if I'm registered in the Voter Registration, I need to unregister, even if I didn't register by myself. Fine, understood. When I get my turn to go to the interview, I'll have to show that I unregistered and never voted. If they ask me why I said "No" at the application, I guess I will have to mention that my father registered me. But if they don't ask me about the Voter Registration I'm not sure if I should or should not bring it up and mention it. Any other thoughts?
You don't need to mention your father. They are aware that people are registered without their knowledge. DMV clerks register people. People who work or volunteer for registration-promotion organizations also do it. Some colleges also do it. All you have to say is that you found out you were registered, and you were registered by somebody else because you know you didn't register yourself.
But it almost surely won't get to that point, for multiple reasons:
1. If you answer NO to that question, they usually don't check if you're registered (it happens, but it's not a routine procedure).
2. It happened so long ago that they probably already removed you from the voter's list even if you were placed on the list back then.
3. Your noncitizenship and lack of SSN at the time may have caused your registration to be discarded as soon as somebody reviewed the form, which would mean you were never on the voters list to begin with (however if they sent your father a voter registration card with your name on it, you'll know it wasn't discarded).
4. If you have unregistered yourself and they checked your registration, they probably won't see your name. They would have to do some deeper digging to find out your canceled registration.
5. If they do that deeper digging, and dig deep enough to get a copy of the form that was filled out to register you, they will see that there is no signature or it wasn't your signature (unless your father was good at forging your signature). In addition, if your father was smart enough to NOT say yes to the "I am a US citizen" on that form, that further mitigates the situation.
So all you need to do now is (1) Find out if you're registered to vote (2) Unregister if you're registered, and get a letter confirming that you didn't vote (3) Say and do nothing about it in the interview unless the interviewer claims that you registered.
B)It's been said that I was not required to register at Selective Service because of the nonimmigrant status, and I'm registered even if I didn't register by myself. And that there's nothing wrong with being registered. Fine, understood. However, since "there is" a registration, even if I didn't submit it and I wasn't required to register, and this registration can't be cancelled, my doub't is if they will see the answer as a lie, the fact that I wrote "No" or not provided the Selective Service Number which actually I don't have and never had in my hands.
You answered NO to the nonimmigrant question. That question then says, if you answered NO skip to question 34. That means if you answered NO to Q33, they expect you to leave your Selective Service number blank even if you actually registered.