Maulik, unfortunately your questions is not very clear. Would you mind explaining how you are trying to add policies to an API product?
Generally, policies are added to API proxies or shared flows and API proxies are added to an API product. It is not clear how you are trying to add policies to an API product:
Moreover, a shared flow associated with a Flow Hook will get applied to all API proxies deployed in the given environment. Hence, shared flows associated via Flow Hooks will not get directly attached to API proxies: