From what I remember from last year from the NROTC process:
1) If you are not accepted at your top designated school the CNET board will continue down your list of college choices until they can offer you a scholarship at a school where you have been accepted. You should have selected 3 to 5 college choices.
2) A bit trickier. If your top choice has filled scholarship-wise before you are accepted you should be offered a scholarship to your next choice if it has openings. You do have the option of attending your top school w/o the scholarship, joining ROTC, and then applying again to pick up the schoarship halfway through frosh year (this works for NROTC - not sure about AFROTC or AROTC) and I've heard that very often the scholarship is awarded then 'cause your ROTC CO can help you there.
3) Go ahead and call the 800 numbers on the scholarship sites. The folks there have always been very helpful and you can run through all your scenarios with them.