If a student graduate and get opt visa for working...

You can transfer to the F1 visa
On condition of obtaining university admission, the transfer can be easily null if the applicant fulfills the following conditions:
- In order for a student to be accepted for this F1 visa, the student must complete the following requirements:
- The student must have a place to live
- He must have the intention to return to his country upon completion of his studies.
- That the student studies only in the academic educational institution for which the visa was issued.
- He must have sufficient financial support
- He has strong ties to his homeland (for example, he is linked to a job in his country that returns to him as soon as he finishes his studies, properties, bank accounts, or family)
It is possible to convert that visa into a temporary work visa after completing their studies. Children and spouses obtain the F2 visa, but they are not authorized to work in America.