Depends on the gauge, load and power level. At least a few hundred yards.
a 12 gauge shotgun can shoot about 30 yards accuracy
Depends on the load, angle of fire, terrain, weather, etc.. a couple of hundred yards at least.
Depends on projectile size. # 9 shot probably won't travel 200 yards, but 00 or 000 buckshot or a deer slug might travel over a mile.
In excess of 50 m
Are you interested in knowing how far a 12 gauge slug will travel, or are you looking for the distance various loads of shot will travel?
The AA-12 shotgun shell can reach up to 175 meters per second.
Shotgun by far
That will depend on the size of the shot, and not the gauge. Fired across level ground with the largest buckshot, a shotgun has a maximum range of between 600 and 700 yards. Not a usable range- just the furthest that shot will travel.
The shot will travel a couple of hundred yards, easily.
About 1" past the muzzle.
Depends on the ammunition. Rifled 12 gauge slugs are accurate to about 150 yards