1) Yes free room and board, along with a stipend (I believe monthly). In addition, you can work as an OA up to 10 hours per week to make additional money (~$7.50 per hour, depending on min. wage)
2) January, on quarters, May change this year (source = Resident Advisors (RAs) : University Residences and Dining Services
3) It's fairly competitive, but I know of quite a few people that became RAs. Just depends on how outgoing / fun / experienced you are.
4) I'm not 100% sure, but maybe 20-30 hours?
5) Definitely become an office assistant (OA). It's a pretty good stepping stone to becoming an RA. Also get involved within a residence hall--each one has their own council. These are great ways to become friendly with a Resident Manager (RM) or Hall Director (HD) that can make it much easier to get hired.
7) If you cannot file your taxes by April 15th, be sure to file for an extension.
(Note: I was an OA for 3 years, but never applied to be an RA)