Hi Rishi, According to my research Kheerganga appears to be open. However since the guidelines in India change so often, I suggest you check the official websites before you travel to ensure that Kheerganga is still open. Also I am attaching this beautiful article I found on the Kheerganga trek to help you plan:
https://www.tripoto.com/himachal-pradesh/trips/kheerganga-a-trek-you-wont-forget-5809c378746d2
Hope this was helpful!
Regards, Senneil