Different people have told me different sayings, such as:
1) As long as the F1 application receipt date is before my H1b withdrawn date, there won't be a gap and I still have legal status.
-You are legal to stay though you do not have legal status until your F1 is approved.
2) There will be a gap if the I-20 date or the date of the 1st class is after my H1b withdrawn date. Thus, I am illegal.
-Depends on how long your F1 is approved. If your F1 is aaproved in advance more than 30 days before the first class date (Semester beginning), your status will have a gap. Otherwise, you are fine.
3) The gap should be less than 30 days between when my H1B is withdrawn and the date of the 1st class. In my case, I am illegal.
-Irrelevant to your h1 withdrwal.
Can you tell me which sayings is correct?
Also will applying community college give the visa officer a good reason deny my F1 application since I already have a Master degree in US?
-I do not know, depends on the IO.
If it is denied, will it affect my application for F1 visa in future even if I am admitted to a top university?
-Normally no.
Several friends did not transfer their H1b after they got laid off, but stayed "illegally" for a while to get a job and returned China to activate the new H1B. Is this way better than transferring my H1B (taking the risk of having F1 application denied but possibly remain legal)?
-Depends on how long and how sure you can find a job. You are legal to stay in US until your H1 I-94 expires though you have no legal status after you are laid off, but if you take too long time to find a job, it might affect your H1 visa application outside US.
Is there a way for me to stay legally besides transferring H1B visa to F1?
-You can change it to B2, etc.
Thank you very much for your time.
Tom