I can clear up a couple of things....
Room service can ONLY be delivered to a room. Of course, there's nothing to stop you from taking the tray elsewhere. My teen tried to have stuff delivered elsewhere--no deal. So, she and her friends waited in the hall by the room. The server made her open the door with her KTTW to prove that it was HER room, then gave her the tray. The kids promptly took it up to the pool area (this was late at night after the deck 9 outlets were closed.)
Rainforest room is part of the spa. It is a large room with 3 smaller steam rooms; each has a different scent and level of steam. Passes are $16 per day. Multi day and length of cruise passes are also available, as are "couples" passes. A couple can be any 2 people--mother/daughter, friends, etc. The longer passes are a little cheaper than daily. It is generally not a good deal to buy a length of cruise unless you know you'll use it every day; miss one and you've lost your discount. Each day allows you to come and go as many times as you wish during the day and stay as long as you wish.
Krisann--I PM'd you several times about your thing. I'd like to participate
If you reserve a private room, they can charge you. They tend to be somewhat flexible. If you just sort of "take over" an unused area, there is no charge.
Woody is correct--there is no microwave anywhere on the ship that is available for guest use. The kitchen will warm baby formula/food for you if needed.
Hanging out in Diversions/nightclubs you will not be hassled to buy anything, and you can bring a glass of whatever in. You will be asked once and a napkin will be placed on your table to indicate to all servers that you've been asked. You won't be bothered again unless you flag down a server. Hanging and playing games in Diversions is at least part of what it is there for--no worries.