A. You win the point. Its not required to hit the ball over the net. It can go over the net or around it.
B. Nobody wins the point. This is a let. The point is played over.
C. Your opponent wins the point. Your shot around the outside of the net was not a legal shot. The tennis ball has to go over the net to be in play.
D. This situation is impossible. It isnt physically possible to hit the ball around the outside of the net.