Ultimate Frisbee is the correct way to spell it.
The type of defense in ultimate frisbee is defending.
disc, ultimate frisbee, flatball, plastic spinning thing. 'frisbee' is a company's trade name which is why the sport is called 'ultimate frisbee'.
Ultimate Frisbee is most popular in New Zealand and the United States.
No, you do not have to win by two in Ultimate Frisbee, just first to 13 or whatever you are playing to.