Can one or both fuselage main gear legs be MEL'd on the B747 as well? Or is it an ubnormal procedure every time that happens?
Nope, we need ALL gear at ALL times.
It's possible to land safely with any one unit in the up position but it's an emergency and we certainly can't depart like that.
With the two body gear retracted there's a chance that the aeroplane may sit on its tail after stopping so it's a good idea to get the CoG as far forwards as possible. (Transfer fuel, pax, etc)
With the two wing gear up, there's only a very narrow track width and so you just stop on the runway and do not try to turn the plane at all. Just park it and leave it there.