I dont remember if you can use your AP for fast passes or not. Anyone know? Or can you use your room key if the room key does not include a hopper pass but you have an AP instead? Hope this makes sense.
You can't use your room key if it does not contain your pass. You can only use a pass that was used at the turnstiles that day. So you can't bring someone else's park hopper and try to use it at fastpass. They have closed all the loopholes.