Difference between done and completed

I have completed/done 12th standard at/ in RT college..

here i have 4 questions

1. I have completed 12th standard in RT college..

2. I have completed 12th standard at RT college..

3. I have done 12th standard in RT college..

4. I have done 12th standard at RT college..

are the above all correct? please do clear my doubts

thanks in advance to all the teachers

Regards,

shravan