Some tricky questions there, that I'm afraid I don't have all the answers to off hand!

Calipers are single piston I would assume, but I might be wrong. Discs are around 260mm. I wouldn't imagine they'd bolt to Focus hubs to be honest.

As for the cables, I couldn't tell you! I can try and get a picture.

However, if your Focus already has rear discs, I can't imagine there would be any benefit to fitting these really. I think the Focus stuff is probably just as good, if not better.