CBSE 10th

Hi,
For NIRMA Institute the cut-offs are generally above 90% and experience is also counted in years not just months. See the link below. To score within the 80 percentile on the CAT you'll need a scaled score of 91 (out of a maximum of 300). This translates to 31 questions but only if you answer every single question you attempt correctly. https://www.shiksha.com/mba/cat-exam-cutoff.

If you are from a reserved category, then yes, you can apply for admission here but if not, you are not eligible. Minimum eligibility for admission in PG courses is 50% in Bachelors degree in relevant subject.

The expected CAT percentile cutoff of IIMs for asked category are given below.
1. IIM-A
Sectional cutoff=60
Overall cutoff= 70
2. IIM-B
Sectional cutoff= 60
Overall cutoff=70
3. IIM Kolkata
Sectional cutoff= 65
Overall cutoff=70

You can download Jammu Kashmir class 10th Date Sheet 2020 from the official website of JKBOSE. Follow the above-mentioned steps to download JK Board Class 10 Board Exam Date Sheet 2020 pdf for Jammu Division and Kashmir Division.

Yes, it is definitely compulsory to get higher education for admission to any of college. Only on the basis of class 10th, you cannot get admission in any of the colleges.

If you really want to do astronomy it's very good so study at least physics and maths in class 11th and class 12th. Do a B.Sc in Physics and take a few elective courses in astronomy/astrophysics. After that do your postgraduate studies in astronomy/astrophysics.

It seems too difficult to get any IIM, still, you can try and hope for the best.

It depends on the cutoffs of various University. But with this percentile you can't get any IIM. Aaj per previous years the average cutoff for any IIM is about 80 percentile, but you may get LIBA, Chennai and XIME, Bangalore.

Yes, you will get admission if your CAT score is above 98+. Hope for the best.