Commerce

Dear student, mistakes happen all the time. It is not big blunder. Yes, if you have changed your mind and really want to become an accountant (CA/CS etc), you can take summer classes. I hope you are good in math.
After completing M.Sc, I can say accounts and pure math walk parallel to each other.
Wish you all the best.

You just have some general calculations in commerce stream. Maths is not so vast in this field. You have other options like medical also but since you want to continue with commerce go ahead without any doubts. All you need is to have your basics clear (maths).

Your score in 12th is really good. Composite score which will formed will be moderate. If you are willing to go till the last rounds in the admission process you might get a good college in engineering. Opting out for Commerce will change your whole stream(field). Though there is no harm in doing that but it will be a little difficult for you to cope up if compared with a regular commerce student.

Hi Mridul, it is difficult to suggest or predict any colleges since the merit lists are not yet out. You can check the list below for the college specific entry requirements for an idea
https://www.shiksha.com/accounting-commerce/colleges/b-com-colleges-india

Hi Dhiman,
There are n number of colleges for the same. Here is the link to colleges that you can choose from:
https://www.shiksha.com/mass-communication-media/colleges/colleges-india
However, the best colleges to do it from will be:
DU
IPU
AAFT
Symbiosis Pune
You will have to prepare for theri entrance exam as well.
All the best.

This depends on the course that you wish to pursue, please specify the same.