Science

You can expect for following colleges:
1. Nagaland University, Sasard
2. RLBCAU, Jhansi
3. Central Agriculture University, Imphal.

Both are good options, but according to me industrial chemistry has good scope and placements are good.

https://www.shiksha.com/it-software/articles/your-career-after-masters-in-information-technology-m-sc-it-blogId-4606
On the successful completion of this programme, you can make a career as:
Software Engineer. Computer Programmer. Interface Engineer. Java Developer. Project Manager. Information Security Analyst. IT Consultant. Network Administrator.

It depends in some college, it is necessary, but there are some where it's not necessary. You have to check with individual colleges for that information.

Yes, definitely no doubt about it. Economics is about studying market behaviors and predicting in which direction it will go. While economics has mathematics to calculate and predict the flow but if you have good command on theories you will become good economist. Don't be afraid of Maths, because in economics it is not very hard, in accounts students say it is.

70-90k p.a for BSC PMC Reva University.

Hi,
Yes, you will be taught about business right from the start of your college.

Yes, you are eligible for B.Sc Mathematics.