CBSE 12th

It's a very good field. For taking admission for the course, there are examination taking place in levels as:-
national level, state level, and some private hotel exams.
NCHM JEE, IIHM, AIMA are few national level exams,
state level:- WBJEE, MHCET, etc.
Private exams :- Oberoi step, IHM, Aurangabad, etc.
you have to sit for the exams. if you have queries,
ask me anytime.
Best wishes.

Just prepare a proper timetable. Start focusing on difficult aspects from right today. Create a chart and place it on your wall and divide the syllabus into two parts and once you clear each topic just tick on it and keep going. I followed the same methodology and scored 90's.

Most of the universities offer admission on 6 band, maybe their might be some universities which will give you admission.

Chemistry comes as a basic subject of general study in your first year of course of engineering if you go for almost all engineering courses. But, there isn't much to worry about its just the basic things you have learned in your 11th and 12th that's just freshened up with a little more of knowledge which is never too much to care about. So, if you've got your NCERT books. That's more than enough for the most of the chemistry, you'll learn.

For any degree course you will need to clear your 12th, so you should focus on the same.

Yes, you can but it also depends on yearly cut-off too.