F1 to H1b-can a person work on campus after H1b approve by another company

I am working in my college on F1 status and my H1b has been filed by another company. If my h1b get approves my effective start date will be OCT 1sts, what if I dont start work for the company untill December and and continue working at my college on H1b status is it possible? So can take paycheck from my college? Will it make me out of status? Thanks

If your H1B petition was filed w/ COS and USCIS approves both H1B and COS you will automatically move to H1B status. Hence you are supposed to start working for the H1B employer from 1st October and get paid. Otherwise, you will be on invalid status.

If your petition was filed w/o COS, you can join the employer in December.

Thanks Sujith for your answer so I understand that I cannot continue working for my college if my COS is approved. But is it possible to start work late for my employer without getting paid atleast for 2-3months? or is it mandatory to start work OCT 1 itself? one of my friend got H1 approved from India but he started work for the company very late and he was fine. So is it possible in my case that there is any certain time period that you can start work late for the employer? Appreciate your answer Thanks

Since your friend was in India, he will be on H1B status only when he enters US and that can be delayed. In your case, if the petition is approved w/ COS you will be on H1B status on 1st October and thus you are supposed to start working with that employer.
I am not sure if there is a way you can cancel the approved COS - please have this checked with any immigration attorney or write to USCIS.

OK, Is there any 60-90 days window where after your H1b approval you can be without work. Or it is not true what I heard?

You can start working for the H1B employer from the date mentioned in the approval notice.