How do you push back the caliper on the rear brakes on a golf 2001?

1. Why can't I push the caliper piston back?

Why can't I push the caliper piston back?

The piston has to be pushed directly back into the caliper, any additional force on one side of it will cause it to bind up and not go back into the caliper. Try getting a big C-clamp and then using the plate from the old brake pad to push down directly over the piston.