Yes! You can unstick and re-apply Ohsnap multiple times. If the adhesive gets dirty, wash it with water. Once dry, the adhesive should be as strong as ever, however, the adhesive may start to wear after 6-8 re-sticks.
No! Ohsnap has been designed so that it's easy enough to slide the frame into the up and down position, but requires more force to remove it from your phone. The frame will not slide out of the frame unless you do it on purpose.