Hi Mithun,
I'm currently facing the same issue while trying to integrate the SAP JAM dev edition as part of HCP trial with our C4C test tenant. Any progress on your side so far and some results that you are willing to share?
In my case WOC Feed is working fine but as soon as I try to create a group based on accounts or opportunities I'm getting the HTTP400 errror that you've highlighted above.
Cheers and thanks in advance for any kind of hint
Sven