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

Hii! It not clear from your question as to where do you want to get selected because it depends on what course do you want to persue ahead. 90% is a very good result and you can get into most of the good colleges of India except those which have their cut off beyond 90%. Also you can register for many entrance examinations like CLAT, NEET,etc. the required percentage there is 45-50%.