Answer 2, just copy the install folder ( about 60GB with all the scenery) to portable media and that's it.... The problem is that the Digital Download version checks the key from time to time via Internet... so if he really doesn't have internet, he won't be using it long.
Answer 1, I think if you bought the Digital download version from Laminar directly your key should be usable on both x-plane 10 and 11... The mail with the key should say something like "Thank you for purchasing X-Plane 10+11 as a Digital Download!"