IIT

Starting Salary for and Chemistry postgraduate from IITs varies from INR. 5 to 10 lacs p.a.

A chemist's primary job is to analyze how different chemicals react to each other and develop drugs, cosmetics, and other daily use products. A chemist earns an average salary of Rs. 2, 74,117 per year.

First of all, admission in IIT is based on your JEE Advanced rank, not on the basis of the JEE Mains score. Second thing is that if your SC rank is below 10-12K, then you may get a seat in NIT or in GFTI.

It is applicable for all the categories. Please read it's eligibility criteria.

Yes, he can get admission in IIT-Kharagpur.
Kindly visit this link:
https://www.shiksha.com/engineering/course/m-tech-in-aquaculture-engineering-indian-institute-of-technology-kharagpur-293511

Yes, it is necessary to get qualify marks for getting seat NITs, IIITs amd GFTIs. Even though they are the marks decided to write JEE Advanced you must get more than qualifying marks to get seat in any NIT. Category rank was not helpful in this criteria.
All the best.

Hello Sourav,
The link below gives you the details about the Indian Institutes of Technology (IITs) in India:
https://www.google.com/amp/s/www.shiksha.com/b-tech/articles/amp/iits-in-india-blogId-12884

It's not possible for you to get admission in IITs or NITs.

No, to get admission in B.Arch in IIT, you have to score a good rank in AAT exam. Mains’ result is only for NIT, IIIT & GFTI.