CBSE 12th

If you are interested for NDA, you should concentrate on that.

The major difference between both these field is that IT deals with the application of computing technology to real life processes, while, Computer Science deals with the science that facilitates these applications. To make it short and simple, Computer Science is the creation of software and hardware by using different programming skills. On the other hand, IT is just the selection of the proper software or hardware for the task.
Based on above mentioned difference and your interest you can choose the stream

No. You have to have maths for giving the NATA exam.

You may pursue Bachelor of Journalism and Mass Communication, as the course will help your learn photography. Along with this, the course will provide you knowledge about different fields, so you may become a reporter, a photo journalist, an event manager or an advertising professional, after completing the course.

The best colleges to get into for BSc in Physics are listed below:
1. Hindu College
2. St Stephen's
3. Hans Raj College
4. Miranda House
5. Venkatesawara College
6. Gargi College, Delhi
7. Ramjas College
8. Maitreyi College, Delhi
9. Sri Ventateswara
10. Kirori Mal College
However, you will have to check the cut off list, whenever it will be out.

You can go with commerce stream. It will be helpful.

Hi
You hv not mentioned your stream to guide you further. You can either choose to go abroad right after 12th for under grad or after completing your bachelor's.

maths is the basic need of many courses. if you have interest in it then go and ahead