Well, it is the same flight JFK-YVR-HKG with a stop in YVR. So you can get out or not. If you stop as mentioned the Skytrain will be shutdown until 5a.m, so you'll need to stay at an airport hotel and I would rec. the YVR Airport Fairmont as it is right beside the terminal (just walk through the doors) and is one of the best airport hotels anywhere in my opinion. F is always better - especially on CX which has one of the best, but J on CX is pretty nice as well if you want to save some points and just sleep. It is usually the new J on the 777s Nice itinerary!