I first fail +2 there after I get 90% can i selected
The admission to Indian Institute of Space Science and Technology, Trivandrum takes place solely on the basis of JEE advanced scores and JEE's eligibility criteria states that the canidates appearing for the exam must have secured atleast 75% marks in plus 2. Therefore, you are good to go, there will be no issues with your selection provided you secure the cut off marks in JEE advanced.
For details regarding JEE advanced cut off for this college kindly visit the link shared below:
https://www.iist.ac.in/admissions/undergraduate