Windows Invariant Culture Puzzle

Question

I have a question about the windows invariant culture.

Succinctly, my question is:

does there exist any pair of characters c1, and c2 such

Answer 1

"However, I don't really have any idea what kind of mappings the invariant culture does, other than the fact that its what windows uses for comparing file names."

I didn't think Windows used the invariant culture when comparing file names. For example if my culture is English then I can name two separate files turkish and TURKİSH, but if someone's culture is Turkish then I hope Windows won't let them do that.