Does anybody know what is a correct position of the arm? It came with no manual but as far as I know the arm should be as far as possible close to 90 degrees to a string. And the tip of the arm should be as close as possible to the arrow.
But this rest has a small bump at the tip of the arm. So the question is how to deal with this tip. Should it hug the arrow or support it?

My rest is A.S. REST OLIMPICO Z/T MOD.C (http://www.arcosportspigarelli.com/prodotto/a-s-rest-olimpico-zt-mod-c/). And arrows are easton a/c/e if that's important.

Thank You.

Played with it a little. It seems the hook doesn't affect the shot. At least I decided not to cut the hook but still have a quite a nice group in the target.

Another question is how far the tip should be from a plunger button? I can put it almost below the button or I can move it about 1 cm farther to the clicker. Which position is preferable?

Some stick on rests have a round hole in the backing plate so the arm of the rest has to fit at a set position below the button, If they have got it right, that would seem like a good place to fix yours.
Some rests use a long slot, but I think that is to allow for the body to wrap around different designs of riser.

Mine has the long slot. So I can move it back and forth quite far.