Science

Hello,
To pursue Bachelors in computer application (BCA), mathematics is necessary regardless of whether you had science or commerce in class 12th board examination. However, there are certain colleges where the rules are not so stringent and they might accept admission in BCA without mathematics.
I hope it helps.

I think, mathematics is not mandatory to pursue graduation in Biochemistry. You can go further with PCB.
Best of luck.

You need to complete class 12th with physics, chemistry and mathematics to be eligible to enroll for TNEA exam.

Mechanical engineering will not be suitable for you because it is based on physics. You can go for CS or IT. These are also good streams and doesn't involve physics. Otherwise, if you can study hard, then you can go for mechanical.

No, there is no branch of biotechnology. You can pursue Diploma in pharmacy and chemical engineering. But, after completing Diploma in engineering, you can pursue B.Tech in biotechnology.

You are not eligible to do M.Sc after completing Diploma in Engineering Computer Science because Diploma is not equivalent to graduation degree.

Hello,
I think, you can go for Master's degree. Is it not a good idea to complete your Master's degree from IIT or IISC? Everyone dreams about studying at IIT. There is an exam called IIT JAM.
You can check the below mentioned link to be familiar with the IIT JAM paper pattern:
https://scoop.eduncle.com/pattern-marking-cutoff-for-iit-jam

Hi Prapti,
Different universities have different requirements. Some are more competitive and selective. So, you should visit the university website for the admission requirements. You can apply, since you have done BDS. You have to take IELTS or TOEFL, submit a personal statement of your career objectives, and submit reference letters. The other components will be mentioned on the university website.