kandy17 said:
I am under the impression, that once Alien number[A#] is assigned you are with in the Quota?
This is incorrect. Several years ago (some oldtimers might remember this), all of the EB dates became current since so few people were using CP and INS wasn't using up any visa numbers (since they pretty much weren't ajudicating AOS cases).
A lot of Indian- and Chinese-born folks with approved I-140s took advantage of this to file an I-485 and remain in legal status (remember, this was pre-AC21 so there were no 7th year Hs back then). After about four months, INS started using EB IV visa numbers and the dates retrogressed back to where they used to be.
Clearly, if everyone with a filed I-485 already had a visa number, these I-485s could have been ajudicated with no special processes . What ended up happenning was that INS had to segregate all the I-485s based on priority date and could not touch those I-485s with a non-current priority date. This would not have happened had a visa number been assigned upon I-485 filing.
Second, visa numbers can change "pools". Let's take my example. I'm an EB-3 professional worker and my wife is my dependent. My class is E37, and hers is E39. Let's pretend that she too had had an approved I-140 and filed based on that; we might have both filed in the E37 pool, but midway through she decided not to work and amended her I-485 to be my dependent. That would change her pool to E39, impossible if the visa number would have already been assigned.
Third, let me give you a personal anecdote. The moment I finally understood my GC journey was over was when our interviewing officer took out a smart card and logged into a very secure web site. She printed out a pair of pages that had "IV Request" on them. Very few of you will ever see an I-485 ajudicated in front of you, but I did - and one of the last steps is to request the visa number from DOS.
Fourth, a few months ago the INS "I-485 operating procedures" PDF was published here. It documents INS procedures for ajudicating I-485s in late 2001. One of the last steps in the process is to request the visa number from DOS.