can i repeat 11th 12th std sci stream after passing it. can i repeat it from another board if yes what procedure for it?
Yes, it is possible from another board other than the one you have already passed from. Simply apply in that board's +2 with your class 10th marksheet. Although you can go for improvement exams from your previous board. I don't think ICSE allows improvement exams though.
and how i apply with my 10 marksheet my leaving certificate are taken from me during 11 admission
if yes how can i apply they can give me admission?
and it is possible that 12th two passing certificate from different board.