Your account is one-year old, not too old. I don't know what you did in the past and want to erase it but one thing you have know.

Even if you get acceptance from theymos or Cyrus to change your username, your real username will still be here. Only your display name will be changed. Username is a fixed one on the forum (one member = one unique, unchanged username), admins don't change username.

This fact means if I know your username (= old display name too) and use it to search on the forum, I will find you but the result will show you in a new display name.

Them giving you a chance to change your username will completely mostly on your excuse. The "because a lot of people follow my old name" could probably be quite broad; because I assume some people could possibly be requesting a name change to get away from their shady activity. You don't need to publicize your excuse here in this thread though, just make sure to explain clearly when messaging the admins.