Hey sumit,
Greetings. I hope you're well.
1- the percentage in best four subjects include one compulsory language (English or Hindi) and other three core subjects which you had in your school. Subjects from The list A and the list B should be included. One non listing subject can be included, more than one subject would lead to deduction of 2.5%.
2- B.Com is offered by many colleges, both in North campus and South campus. The cut off is usually high since a lot of students opt for it in regular college. Whether you will get a seat or not, cannot be said with surety but since you're from reseverd category, there is still some chance. You'll have to regularly be updated with the cut off. Also, you might get a seat in evening college, so you can reserve a seat there. In case, there will be a better option for you in further cut off , you can change your college.

Here is a link for you to know the third cut off.
https://university.careers360.com  ...
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