Science

Hi Abhishek,
For M.Sc Biotechnology, you can go for Punjab University, Delhi University. The admission is based on the entrance exam, and the syllabus is what you have studied in your graduation. Also, you can visit their official site for syllabus and admission procedure. As there are limited seats you have to get a good rank. Good luck.

So far my knowledge goes, you can pursue M.Sc Math in some Institute after doing B.Tech Mechanical. For example, Chennai Mathematical Institute allows B.Tech /BE for doing M.Sc Math. They also allow B.Sc Math/B.Math/B.Stat. For M.Sc Maths, you can visit their site for confirmation. Best wishes.

At first, you will be studying the very basic and dominated by what you have already studied in class 11th and class 12th. So, you can actually do both, but hard work is obviously required here. Also, time management is very important.

You can do that, if you have chemistry, as one of the major subjects, as in B.Sc, Life sciences or B.Sc. Physical sciences.

It is best, if you pursue MBBS from abroad (European universities are also good), but make sure those are MCI recognized. In India, it is difficult to pursue MBBS from private universities, because of high tuition fee charged by the colleges. Dropping a year and preparing for NEET will not be a good idea. But, if you are 100% sure about yourself, then you will definitely get admission next year. Go ahead with NEET. All the best.

Yes, best 4 percentage matters.
You just need to have a passing mark in the 5th subject.

Cyber Law Questions and Answers | Cyber Law Mock Test - Vskills
https://www.vskills.in startPracticeTest
Practice mocks, because last year's question papers aren't available.

B.Sc Nursing is not included in NEET, so forget seat in nursing, you will have to go through the entrances.

Sorry, but you can't apply for KVPY. There are 3 streams SA (in 11 class), SB (in 12 class), SX (First year of Bachelor course), but you still have other options, like if you will be able to get admission in integrated Ph.D course, then you can get a fellowship from the institutes, but there are few institutes who give this fellowships.