About Terra's backstory

Hello! This is a question that has been bothering me, so I wanted to know if there some official source out there that talks about this, like interviews and whatnot, because all the wikis I found are not very detailed.

In game we are given Terra's bastory until the Emperor's invasion, but is there anything about her between that and the start of the game? In one of her first remebrance scenes with Kefka and the circlet she looks like an adult, so the memory wipe seems recent in-universe.

Also they mention Terra being a subject of "terrible experiments" once, and never bring it up again. Given Cid's role in Esper studies I thought he may have "raised" her as a Guinea pig, but he spoke only of Celes.

Even things like: is the surname Branford from her mother's side or her adoptive family?