B.Com

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

Hi,
There are various internship opportunities available on Internshala and other internship platforms. You can get yourself registered and mention your preferences so that you get opportunities of your choice. Also, you can try to get some live projects that are offered online. You can also get yourself enrolled in some certificate courses related to your degree for eg. Tally, Advance MS excel, etc. This will give you an edge over others.
All the best.