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.