OPT approved, but will not graduate.

[SChari]

I was initially planning to graduate in December 2020 and had applied for post-completion OPT. Since I realized that I will not be able to graduate, I applied for program extension and sent a withdrawal letter to USCIS while my OPT application was still pending. My program was extended by the DSO. However, my OPT was approved before my withdrawal could be processed (my withdrawal letter reached USCIS a day before the OPT was approved). Will the OPT be revoked at a later date? If I am on OPT next semester, will I be eligible to take up on-campus employment (a graduate teaching assistant position) to satisfy OPT requirements? Also, will I be able to start the on-campus job before my OPT start date since I would have a valid I20? 

If I am unable to find a job that satisfies OPT requirements within the 90-day unemployment period, will I still be able to complete my program (since my program end date falls beyond the 90-day period)?