They compensate for the smaller rear tires. The rear tires have to be small, in order to facilitate turning. The larger tires are used to drive the vehicle, so they need to have a large cross section to distribute weight evenly enough in order to prevent the vehicle from sinking into the ground. The large diameter of the tires also serves two functions - it helps keep the cab elevated above the radius of the head, and also keeps the vehicle geared low enough to deliver ample drive torque.
To provide more traction.
The larger rear tires get better traction in the mud and rough terrain. The front only needs to steer.
Maybe, the manufacturer optimized the tire size to the vehicle, if your currently running larger than stock tires then you could be decreasing your mileage. Check the inside of your drivers side door for a placard with the correct tire size and inflation.
move back tires to front and front tires to back
yes. both front must be exactly the same though and the same goes for the rear pair.
front tires straight back rear tires crossed to the front
If the vehicle is front wheel drive, yes.
On the front tires.
On the front tires.
You have a damaged tire. Try rotating the front tires with the rear tires to see if the wobble switches to the back.
Yes. with larger tires the odometer will show less mileage than actually travelled.
do I have to have two of the same front tires to align it?