for landing, you should go to the cockpit!
ask the ISM or FA as soon as you board the flight (sometimes they ask if you have a name card). they will ask the pilot's permission and you can most likely witness the landing in the jump seat.

landing in HKG is spectacular (but you may want to do so in your shorthaul J flight where F beds are not available)

regarding center seats, there is usually high demand from people who travel together. so most likely they will put you to the window