JEE

Dear,
Following link will give you the idea of the admission procedure that Amity Follows for NRI Students.
http://www.amity.edu/admission-procedure-nri.aspx
Do ask me if you've any more queries.

Yes you can clear jee main because the cut-off of obc category is 61 and for general is 91.

You can use the following links :
https://www.shiksha.com/jee-main-rank-predictor
https://www.shiksha.com/jee-mains-college-predictor

You can try next year, this year JEE main exam is already over

prepare your 11 and 12 sllaybus .

To become astronaut you will have to become a Pilot or Flight Engineer. Opportunities to become Astronaut are very few ( you can count them on fingers). In India astronauts were inducted from Fighter branch of Indian Air Force. I will recommend that complete Aeronautical Engineering degree and learn to fly. You can then apply to organisations such as NASA to fulfill your dream.

There is no separate examination conducted by IIT madras, enrolment in IIT madras is done through JEE advance and its one of the toughest engineering examination across India

You rocked it bro .check out shiksha rank predictor https://shiksha.com

when we prepare for JEE we also get prepared for all other entrance exams. so you get prepared for NID by JEE

allen or resonance or vibrant all threes are good