Couple of question about muscle contraction

[IndoorKid]

Hey guys i got a couple of questions about muscle contractions that i'm a little bit lost on.

- why does skeletal muscle contract more forcefully when stretched?
- when a muscle is stimulated repeatedly what happens to the force of contraction? and what is the mechanism behind this event
finally
-what happens to muscle at the highest preload forces.

I've had to do a bunch of questions on this and these are the 3 that i just can't answer.
Hope someone can help

[IndoorKid]

spoke to a tutor who helped me answer them
thanks for your time