With all the work that Susan has done on the Forever Knight wiki, including 32 challenges, we do not appear to have any information (yet) on the Center Stage Challenge. Sorry about that. Maybe someone who was active in fandom back then can help you more.

We have a remarkable number of factions listed. But we don't have any collective term for Nick, Schanke, and Natalie. Also, we have "Dark Trinity" listed as the faction you call the Fang Gang! (Honestly, this is quite a prolific fandom, isn't it?—terminologically speaking.)