Is it possible to study only physics subjects in BSC-MSC deeply while enrolled in the B.Tech program?

Frankly speaking, Do not let your schooling interfere with your education. Now, i do not know any college which gives you the flexibility of studying only subjects of physics, but no one is stopping you from doing so in real life. I have a friend of mine, who dose not like Computer Science but is doing Computer Engineering. He keeps himself same by study physics which he loves. I have had a lot of fun time chatting with him, and discussing physics. Use the Mooc's to your advantage try http://www.coursera.org http://www.edx.org Udacity Mit Ocw Nptel

Well you can study whatever you want as long as you can focus all your attention to your exams in that last month. Study what you love. Now coming to terms of it being possible , I don't think any university can put so much workload  that you can't find time to study as per your interests. Declare a time zone for yourself and time your studies. I studied very hard during my first year of graduation. Then I realized that although I was in a stream of my choice, the subjects were too digressive. So, I declared the last month before exams as the "study university subjects" period. Rest of the semester I do whatever the hell I want. As long as you play it safe and smart, it's good to follow your dreams.

There is no college that has such a course in its curriculum but ya you  can go for it if you have an interest.You just need to prepare at the last moment for your examinations and rest all time can be utilised in whatever you feel like doing.