Tom got a 2 parter (kinda) for you: 1) can Mystique make herself look however she wants, or can she only turn into people shes seen? 2) Does she gain some sort of knowledge of that person's life when she transforms, or does she do crazy research prior to becoming someone that just is never shown in the books?

Anonymous
1) Mystique can make herself look however she wants, she needn’t mimic specific people.
2) No, in assuming their appearance, she does not gain any specific or hidden knowledge concerning who they are.