On question no. 2, you can also change the full name using control userpasswords 2, selecting the username and clicking on properties.
For 3, the problems aren't caused while using system restore, but the rescue console. If you boot from the CD and try to access the rescue console, it asks you for the admin password (no username, just the password). That's where you're screwed if you need to use the recovery console.
Cheers,
cgkanchi