What happens if both parties violate a restraining order?

No, but violations of such do. A restraining order is a civil order.

If you filed the restraining order, you can withdraw it. You must go back to the court where you filed the restraining order and ask that it be dropped.

No evidence is necessary for a temporary restraining order. What happens is when you go into court and get a restraining order they give a temporary restraining order until trial. You can then push the date back a few times and extend it. Some people would argue this is how you get custody of children in a divorce situation. For a long term restraining order you will need documented cases of abuse.

Depends on the reason for the restraining order but I don't think, considering its temporary for whatever reason, it would count as a criminal offense.