Through the ticket system. It's not top priority especially for newer members, so you'll have to be patient
I was under the impression that this service wasn't offered. I thought I remember reading about it years ago saying that there'd be too many requests and it would be confusing.
I see name changes still.. Usually the only users who get a name change have been here for more than a year, and even then it's unlikely
Interesting, must have been remembering something different. But yes as BYOweed mentioned, if it's possible then you'd do it by submitting a ticket, but prepare to possibly wait a little while, the moderating staff is really spread thin already as it seems.
Lowest priority because only one person can do it and she's a super busy lady. It's so low that you shouldn't get your hopes up because there's a good chance it won't happen.