Biotechnology

Hi
It does not matter what kind of internships you do for CAT exam, although it matters if you want to do job in biotech. Work experience is counted for CAT and not internship experience. Secondly, you can start preparing for the exam in your last sem or last year. If you are really impatient then start solving GA questions from previous years. And most importantly focus on your college %/CGPA/SGPA. It should be very good.

https://www.shiksha.com/university/university-of-madras-unom-Chennai-23679/admission
This link will help you.

Hi
No, you cannot do M.Tech in food tech as the requirements are completely different. There is no Masters+PhD (food proc) programme in any college as Ph.D requires clearing UGC NET exam. You should pursue M.Tech CS which will give you better packages.

Taking up a Ph.D will certainly boost your career prospects. There is no need to qualify NET exam for the same. You may need to appear for the entrance exam conducted by the institute. After M.Sc you will find opportunities in research laboratories, pharmaceutical companies, chemical industry etc. If you want to make a career in the research field you must appear for the NET+JRF exam. Normally candidates join any of the research firm as research assistants and prepare for the NET+JRF exam. On clearing this exam they are eligible for the pay scale under the UGC norms. After this they pursue a Ph.D along with their job.

Refer the link:
https://www.shiksha.com/engineering/colleges/b-tech-colleges-india

Yes, but you have to write JEE Mains.

The rank needed is below 3k.

For B.Tech, you need to qualify an entrance exam like JEE Mains and for M.Tech in IITs, GATE is must.