I have not worked on any 747s and can't answer specifically on their truck positions at touchdown, but I can give you some "generals" related to your other questions.
The wheels are not spinning before touchdown. They experience a high amount of friction at touchdown, obvious in the puffs of smoke at touchdown. Some systems rely on wheel speed to activate. In many aircraft, the anti-skid system is dependent on wheel speed and won't even activate until the wheels spin up over a certain speed (like 50 kts), and then disengage as the aircraft slows down to a ground speed of about 25 kts. When it detects a wheel is locking up (one wheel's speed compared against the others), it will relax the brake pressure for just a fraction of a second on that wheel to allow the wheel to regain traction and then re-engage normal brake pressure.
Many of the aircraft's systems are tied into specific wheel position. On highly automated aircraft, where the actions of a system depend on an "in air" or "on ground" condition, the aircraft could depend on a "squat" switch in the main gear, nose gear, or both to determine if the gear is extended (as in flight) or compressed (as on the ground). On an MD-11, I know of an incident where someone was refueling an empty aircraft, and began with the tail tank. As the aircraft became tailheavy and started to pivot back like it was going to sit on it's tail, the nose gear extended, making the fuel system think it was "in the air" and began transfering fuel forward out of the tail to get the aircraft back into proper CG for level flight. You see, the fuel system controller on the MD-11 is also responsible for CG management by controlling the fuel in the tail tank.
The groundspoilers and reverse thrust systems are usually also tied to either the wheel speed, OR the squat switch to prevent an in flight deployment.
After take-off, there are wheel brake pads located in the wheel wells (on most aircraft). As the gear is retracted up into the wheel wells, the wheels contact these pads which stops the spinning.