Maths Spl

Dear Manas,
If you are so good in mathematics and science then I personally believe you don't need to go anywhere for a job. You can start your own tutorials. Earnings through tutorials have no limit. In fact, you will have to keep people in the job to assist you. However, right now focus on your studies and complete your academics.
I hope this would suffice.
All the best.
God bless you.

There is no specific guide book for TUEE. If you study the books by NCERT on your subject it should help you prepare for the TUEE or you can also go through Physics Today, Chemistry Today, Mathematics Today and Biology Today. These should help you prepare well for the TUEE. You could also download previous year question papers and sample papers of TUEE 2018 for your exam practice from the link provided below:
https://www.shiksha.com/university/tezpur-university/exams/tuee/question-papers.

You cannot apply for courses like BBA if you didn't take maths in your SYJC.

Yes, maths is necessary in 12th standard for IIT. As you are interested in Biotechnology, please search for institutions, which don't require maths as a subject.

If you are interested in science and maths then prefer to take admission for 11th science.

I would suggest NIT-Agartala over ICFAI for M.Sc in Maths. Not only this is a government college, but also the course fee is way less than ICFAI.

You can be a pilot regardless of your stream in class 12th, you just need a 60% in Physics and Maths in class 12th. In case you did not have these subjects in class 12th, you will have to apply to National School of Open Learning and appear for an exam and get a passing certificate for the particular subject. In your case, you had Physics, but not maths, so to be able to be eligible for Commercial Pilot License course, you will need to clear Math exam from NIOS first.