1. At a guess its only an option on the aircraft that use EPR as a measure instead of N1. If you lose the EPR indications for some reason you can fall back to control through N1. This wouldn't be relevant on an N1 controlled engine.
2. Pass
3. Autopilot takes care of rudder trim when enaged.
4. Sounds about right.
5. Depends. I'm assuming it means holding the priority button down for a defined period in order to take control of the aircraft through your sidestick. The othe sidestick is then locked out until they press their priority button.