Birth by Sleep The dark soldier

I don't think it will be that big. All it is, is that Ansem realises his mistake and orders his apprentices to destroy all the research, whereas instead, Xehanort steals it, and continues it. What I do want to know though is whether Xehanort did the research to himself, or if the other 5 do the research to him, because I never found out how he became a heartless + nobody in the first place.