CBSE 12th

Yes, you should have to prepare for JEE Mains as it will provide you an opportunity to take admission in the colleges like NIT, IIT and also in other colleges.

Hi Sahabaz, some popular options after biology are:
MBBS
BHMS
BAMS
BDS
B.Pharma
B.Sc biology
B.Sc Nursing
You may check more career options by choosing the relevant options here:
https://www.shiksha.com/careers

Hi Richa, you are pretty clear with your goals and aspirations. Since, you have decided to opt for earth science, you can look for Bachelor degree in geology and further gain Masters in earth science and a Ph.D if you wish to study, research and explore further. Coming from a PCM background will only help you understand the concepts.

Hi Abhishek,
Arts is a wide field. Here are some popular options:
BBA
BMS
BA English, political science, history, geography, etc.
B.Ed
BA Psychology
BA Economics
B.Des
BFA
BA LLB, etc.
Choose as per your interests.

National Law Universities are the best institutes for five years LLB degree courses. If you are able to crack CLAT then it's the best option to become a lawyer. You may refer to following link for list of top law colleges in India: https://www.shiksha.com/law/ranking/top-law-colleges-in-india/56-2-0-0-0.
You may select your college on ranking of college not on whether it's government or private university.

All B.Tech CSE students undergo basic courses in programming languages, data structures and RDBMS initially to put all students on same level. You will not face any problem or challenges if you did not have computer science as a subject in 12th board exams.

The entrance exam of NID is held on second Sunday of January and the entrance exam of NIFT is held in mid of February each year.
All the best.

Choose BCA. This course has a large scope across all over. I am currently pursuing IT engineering. Those guys have better knowledge than us. Also, in their course it is compulsory to have to do 6 months internship in MCA. If this is not for you then go for management courses like BBA.
Thanks.