I'm effectively a member of Group C (if type is not inborn, it arises so early in the first year or two of childhood that it makes no difference in practice). However, the question is hard to answer because I'm not sure what you mean by "realistic impersonation of a false type". If you mean like an actor on stage or in a movie, then yes, it's possible for a skilled actor to realistically fake another type. There might be some types which can't be faked in that way (I suspect it would be hard to convincingly impersonate your Conflictor or Supervisor, due to the weakness of the Vulnerable function), but certainly it's possible for some types.
However, if you mean faked in the sense of living and interacting with people in real life, long-term, and convincing people that you're competent in areas in which you're really not, then no. It might be possible short-term, but eventually your lack of ability to improvise and innovate in your weak functions, and your unease with your unvalued functions, will show through.
People do wear psychological masks (Jung's "Persona"), but these can't entirely hide one's inner type from a keen observer.
In other words, you can fool some of the people all of the time, and all of the people some of the time, but you can't fool all of the people all of the time.
I'm just not sure which poll option that makes me...