CBSE 12th

You can become a scientist and go for the research field whether by doing B.Sc or by attempting KVPY, one of the prestigious examination in India in the field of research. You can go for KVPY in the 1st year of your graduation.

Hi,
There is no harm in doing your 12th from Haryana state board. DU is a centrally funded organization (This is not a state university where you will face any state quota) and hence every state is equal here. You just need to score above 98% or 97% in 12th to get seat in a good DU college.

Yes, but it happens rarely.

If your annual income is less than 1 lakh you can get scholarship. Otherwise scholarship for meritorious students is also available.

Try going for coaching classes for Physics - the number of students must be less so that the teacher can give you more attention.