Dear Kishan,

For SA stream: You must have secured a minimum aggregate of 75% marks 10th standard.

For SB stream: You must have secured a minimum aggregate of 60% marks in 10+2 examination.

For SX stream: You should have studied Mathematics and Science and secured a minimum aggregate of 75% marks in the 10th standard.

I think this will give you an idea about the eligibility of each stream. 

And the notification of KVPY is released in the month of July. So, you can apply for it even if you passed the 10+2 in 2018.

I hope this will help you.

Good luck