I'm pretty sure the A380 can land anywhere a 747 can. EK fly the A380 to both the east and west coasts of the US, so they must have some alternates.
Yes, but the aircraft (a) might not be able to depart again and (b) leave 500 people stranded with no stairs or other infrastructure in -50degrees in various Central Asian -stans.
747 is a lot more flexible.