CBSE 12th

Yes, you can. Participate in the counselling, and opt for a good college. You have scored enough marks in JEE Mains and class 12th to get admission in a good engineering college.

If you want to become a doctor, you need to prepare for the PMT otherwise, no need to prepare for PMT. There are several government colleges which have biotechnology as a subject. They select student through merit list based on their percentage.

This might not affect while placements because that time they'll put more emphasize on your post-graduation marks. But yes, this might affect your admission for MBA. You can still get into IIM's if you score decent percentile and do well in GDPI. Your graduation marks might be a bit problem but yes not all the IIM's give as such importance to graduation marks. Try to score above 99 percentiles in CAT and do very well in your GDPI for getting into IIM's.

There are a lot of professional courses, Diploma and certification courses available. You must first decide what you want to do or in which field do you want to go Some of them professional courses are CA , CS , CMA , CFP ,CPA , ACCA ,CIMA , ACTUARY and diploma courses are wealth management , financial accounting or you can prepare for competition such as SSC CHSL , Clerk

You should continue with the stream you took in class 12th for better career prospects.

You can opt for engineering, computer or aviation courses. All the courses have a good scope. You can avail n number of career opportunities after completing any of these courses. You just need to work hard.

Hi,
Belonging to a certain stream won't really hinder this aspiration of yours. If you have done your 12th, do your graduation from a recognized university. Prepare for civil service exams. It would be better if you could look for a coaching (HT's & Byju's classes offer this kind of coaching).
Prepare for it with full seriousness.

Just find the area of your interest first that in which field you are interested. Don't look for job or scope right now because if you give your 100% in any field (Science, Arts, Commerce) you will probably get settled. But you must first decide what you actually want to do, don't think for job right now.

It depends on your interest. After 12th with maths, you can choose B.Sc or B.Tech in mechanical branch as it is having the best scope.