B.Com

You may refer to the link below for top colleges for B.Com (H):
https://www.shiksha.com/accounting-commerce/ranking/top-commerce-colleges-in-india/97-2-0-0-0.

Please mention the college you wish to give this entrance exam for so that I can guide you better.

Yes, for LLB. Your graduation marks will be considered for admission.

You can do a Master's degree in management, Master's degree in commerce, a Bachelor's degree in law, CA, CS, CMA, etc after this course.

Hi Bharat, Yes, you can. The eligility varies from 55%-60% from college to college. DSE, MSE, IGIDR, JNU, GIPE, etc. all offer Masters in Arts. You'll have to prepare for their specific entrances. Each college has a different pattern of examination. I suggest you go though their website and check the scheme of examination as well as Google the previous years and prepare accordingly.
Hope this helps. Good luck!

You can give CLAT exam to pursue LLB (Bachelor's degree in Law).

PGDM is equivalent to MBA. MBA is a degree provided by any university while PGDM is affiliated to AICTE. Even IIMs provide PGDM degree. Both are good, the only thing is the institution from which you are pursuing it.

DU JAT is not for B.Com (H) course. Please refer to the link below to get a better understanding:
https://www.shiksha.com/university/university-of-delhi/exams/du-jat