So I think there are a few considerations, but ultimately, yes they have a finite amount of openings. Beyond this you have people from, potentially, all over the country applying which makes the applicant pool much bigger. Then there are UCLA nursing...
Don't think so but I wouldn't stress it too much. If/when they interview they tell you the unit and it's totally possible despite whatever you applied for you get an interview with another unit.
Not for all units. I had 2 interviews for one of the units. Basically all behavioral questions for both. First was with managers second was with panel of nurses from the unit. Other units I believe are just one interview though (I think the majority)...