Bachelors

Please clarify your question. Why do you want to change your stream if you have already planned to pursue UG in commerce?

Hi Balaji,
If you have great scores you should try Germany, a hub for automobiles and mechanics. Also, education is almost free, if not free then very cheap and they would charge only semester fees. Additionally, living expenses would be incurred. Check RWTH Aachen, University of Heidelberg, University of Stuttgart, etc. You may also check universities in Spain and Netherlands.

Apart from NDA, you can also go for the other options which are available like you can give the exam of SSR for Indian navy after 10+2 (science stream). So, there are various gates for the entry.

After Bachelor Degree, you can go for Masters & PhD
But, all depends on your desire. You can also opt for Professor or a taxonomist or even research scholar.