It's still a legal obligation for males between 18 and 25 to be registered for the draft, if the need for it comes. It won't. That doesn't free you of your obligation, and selective service will still prosecute you for refusing to sign up for selective service. They will keep harassing you, send you emails, mail, threats in the mail, and show up at your doorstep. If you still refuse to sign up, they'll prosecute you for a felony.
Uhhhh
To be honest idk if I did. Is it linked to voting registration in any way?
Usually when you register to vote there's a separate section on the forms to sign up for selective service. I did mine separately so I didn't have to fill in that part, but I remember it being there.