A fumbles and the ball is nearly at rest on the B 3 yard line. B applies a new force (let's not debate if its a new force or not, in this situation I've ruled that it is
) that puts that ball into B's endzone. B picks up and possess the ball in the end zone (B is not "down" when he possess is it).
What can happen during:
a) a normal scrimmage down
b) a try
c) OT (normal Fed 10 yard line OT)