Biotechnology

B.Sc+M.Sc+Ph.D (BT) is a science stream course available in all major arts and science colleges whereas B.E. / B.Tech. +M.Tech+Ph.D. (BT) is an engineering course (more applied) which is to be pursued in an engineering college/ technical university. Career prospects are different. Option: 2nd is better, but costlier than the earlier one.

You need to take CET or ComedK to get admission in this college.

You may get admission on low marks. 70%+ marks is good score.

Congratulations on getting good marks in PCM. For biotechnology branch with low fee, I am able to think only of government colleges. So, can you please tell me that have you given or are preparing to give JEE Mains? If yes, then get a good rank in it and you can go to India's top engineering colleges with low fee structure. If not, you can try for various state government colleges like RGPV, RTU, etc. You can get one of the best state government colleges.
Feel free to ask more questions.
All the best.

I hope this link will help you:
https://www.shiksha.com/university/techno-india-university-kolkata-38061/courses/msc-bc

When you are interested in mathematics all the branches of Engineering are related to it. Only chemical engineering deals with chemistry so it is not a good option for you. All the branches of Engineering depends on mathematics and it is taught in each and every branch for first 4 semesters and in rest of the 4 semesters there will be a lot of use of maths in each and every branch.

Both have good scope. All depends on your area interest. As a Biotechnologist you may be involved in both wet lab and dry lab work where as Bioinformatics it will be purely dry lab.

In India, currently there is more importance given to biotechnology and there are so many vacancy for this too. I would suggest you to go for biotechnology. It is a blend of emerging technology with used for biological systems. It is easier to go into Forensic Science or Marine Biology or Environmental sciences or Pharmaceutical Studies with Bachelors in Biotechnology.
For salary, it depends upon the field you have specialised in. If you decide to join industry then biotechnology is more fruitful than microbiology.