Not sure when we switched over. it used to be wired to the chassis battery, so yes you would need the key in (not on, just on Accessory). However at some point we started wiring it to the house batteries.
If you have the switch box, that DVD will play to any TV. Unless of you have the 3170, then the middle kids room TV has its own DVD player.
PLEASE do not send questions via Private Message, my inbox fills up too quickly. Post questions in the forum as a new thread so that other users can benefit from the answers. Use Private Messages for sensitive information only (VIN, Contact info or things you do not want the public to see).