Not intentionally, no. But, a neck bent a little forward or to the side will block the airway and restrict the air passage.
nope, if that were true people would be dying in their sleep by the millions everynight.
In fact the holding the head back with neck extended routine is really only better at helping flood the victims lungs with water.
Don't bring a convulsing diver (oxtox or whatever) up because they can be involunatrilly holding their breath, wait for them to stop (good stop or bad stop) then bring them up. I recommend being less concerned with form than control and speed of assent. That said in class forum is a great thing to strive for and mark against.