Thanks cerrium, please tell me if my understanding is true:

First I get a H1b from school as a postdoc(not under the cap);
once got it, immediately I can leave the school and work for a company
(whose H1b comes under the cap),
the HR will handle it while I can work legally.

If this works, everyone can do this to circumvent the H1b cap.
There is something illogic here, what is wrong?

but I still confused:
Since some people told me that this way works, some said no.

Thanks for lionfish and cerium, now clear about H1b quota.

I am going to apply for a research associate position next June, that will be a H1b from university. So shouldn't have the quota problem.

My concern is about my wife, she got Master degree, is now in opt, till next Oct. Passed qualified for Ph.d, and the department welcome her back anytime, so she has the option to go back and get an assistantship. But then we have to separate.

If I can get the H1b visa from university in June,
then I start to apply for GC right away,
maybe EB2(NIW). If that is the case,
do you guys think it will take more than 18 months from June to the point I file 485
(I heard 140 & 485 can file together), so it won't be long?

Is that true, once I file 485, my wife can work legally as H4 as long as the
GC application dosen't get rejected?

In this case, she better keep her F1?
Then change to H4 afterward?
or just keep F1 until we get GC?

If I apply for GC when I am H1b and she is F1, but get rejected.
will she be out of status?

Sorry for posting too many questions, thanks you guys for your patience.