A) Yes
B) Never
C) Never
D) Never
Sheep are easily panicked, and the flock will follow one sheep who looks like a leader. The leader usually has no idea where to run, though.
If the sheep have nowhere open to run to, they will run, panic-stricken, into hedges, fences, whatever is in the way - and injure themselves.
If the leader decides to jump over a low spot in a hedge, every single sheep in that field will follow that leader.
If the leader "sees" an obstruction that isn't there, and makes a desperate leap over it - every following sheep will jump exactly the same height, in exactly the same spot. Sheep can jump surprisingly high.
If the sheep have a large field to disperse into, they will follow the leader to a safe (to them) distant spot in the field, and then they will all stop and turn and watch you.