Igor,
Thanks for your post!
Your question is fairly broad-ranging, but it seems that the basic information you are seeking relates to one's odds when applying in R3 to schools like Stanford, Berkeley, NYU, UCLA and USC.
In order to properly respond here, we'll need to first divide these schools into two groups:
Group A (schools that have three rounds of admission)
-Stanford
-UCLA
-NYU
Group B (schools that have four rounds of admission)
-USC
-Berkeley
As you might guess, a third round application in Group A is going to be much more challenging (from an admissions standpoint) than a third round application in Group B. This is because in the case of Group B, you will not be applying in a program's final round. As to Group A, you should keep in mind that programs like Stanford - arguably the most competitive MBA program on earth - typically have very few slots available by the time they reach their final round.
Remember that all the leading MBA programs openly advise applicants to avoid an application in the last round - since the majority of admissions officers like to build the bulk of their class with applicants from the early rounds (rather than wait and see who shows up later).
As to how this all pertains to your specific candidacy, that's a harder question without knowing more about you. On a very basic level, your odds at Stanford are going to be very low in the final round (no matter what your background). NYU and UCLA will not far behind Stanford in terms of admissions difficulty for the final round. Of course, your chances at Berkeley look a bit better, since you'll be in the third of four total rounds. The same is true with USC, which presents the best overall admissions odds when compared with Berkeley or any of the other programs on your list.
Clearly, if you have a truly remarkable and incredibly unique candidacy, anything is possible. Having said that, you should go into the late rounds with your eyes open about the low chances for admission.
Best of luck,
Graham
