A casino comp is a free item or perk given out by a casino to entice you to play more. To earn casino comps on a Royal Caribbean cruise, you must first spend time and money gambling in the onboard casino, Casino Royale, being careful to use your Sea Pass cruise card to track your play.
In general, the most popular spot to be on a cruise ship is midship on a higher deck because these rooms are centrally located. Moreover, cabins towards the middle of the ship have the reputation of providing a smoother ride when the ocean is rough.
Technically, you can..... but the cruise line will discourage it for obvious reasons (if the A/C or heat is running, you get the idea). If you leave the door open, your cabin steward will keep shutting it. We turn our air off this time of year while cruising, and do sleep with the door open.
Midship staterooms on the lowest passenger deck are the most excellent spot to be on a cruise ship in this instance because you don't feel the vessel sway as much.