JEE

The Eligibility Criteria (Qualifying Exam) is Pass with 50% aggregate marks in 10+2 with English, Physics, Chemistry and Mathematics and pass with 50% aggregate marks in Physics Chemistry and Mathematics, subject to qualifying marks in NATA 2022. or Pass with 50% in Diploma (any stream) (3 years) re

Go for ISRO, ISRO is having specialised recruitment board ISRO Centralized Recruitment Board (ICRB) through that you can get into ISRO. Please check ISRO website careers page for job opportunities. I don't have much idea about NASA. Hope it helps.

For the year 2020 , 112 marks ( 28.28 % ) out of 396 was closing marks in general category. But this marks will vary from year to year depending on paper difficulty and the students who applied for IIST. In terms of rank , you can have target of getting rank under 10k as of now.
Hope it helps.

You can check the following link for more information -https://www.shiksha.com/university/iiit-hyderabad-international-institute-of-information-technology-53885

I would recommend you to make use of YouTube as well as some study material provided by some coaching institutes. You can borrow the study material from your relatives or some friend who have already passed his year.

Visit the rank predictor of Shiksha from the link given below-https://www.shiksha.com/college-predictor
and also sit in exams of few good private colleges.

Yes, NIT and IIIT take admission on the basis of performance in JEE Mains.

Because JEE is bit tricky which requires proper understanding as compared to other engineering entrance exam.

You can refer to the following for more information -https://www.shiksha.com/engineering/articles/jee-main-2022-registration-application-form-blogId-72813.

You can refer to the following for more information -https://www.shiksha.com/engineering/jee-main-college-predictor.