I got 65% mark in 12th can I make free seat admission in computer engineering

Hello Rahul, getting admission just on the basis of board is almost impossible. You can apply for DU but you won't get selected there because the cutoff is very high at about 95%. You won't get any government engineering Colleges because they require JEE Mains marks for admission. So if you have given JEE then apply through that, otherwise take admission in private college through management quota.

If your marks are not good or you didn't score well in 12th but want to get admission in computer science engineering then there are many good college in which seats remains vacant after admissions. You can take your admission there. There is no any problem with 65% in 12th.
Good Luck!

Yes definitely!

You are eligible for the entrance exam JEE which requires a minimum of 50% for admission to various engineering colleges.

However, to get admission, one has to crack the entrance exam JEE or other state level entrances.