Edit: whoops, missed your first first question. Yes, fred et al come from Proto-Germanic frithuz, which is constructed from frijaz (free) plus noun suffix -thus.

Well as for the first second one, language families tend to have different roots for the same thing, of which different ones will become preferred in different regions. Both of these words actually work in both Russian and Polish, it is just that one of them is archaic.

As for the second third one, I don't think they're supposed to be the same colour. As far as I know, they are unrelated.

For your third fourth question, no clue. I might look into it someday.