Is there any Facebook Graph API to search all public posts containing a particular hashtag?
Example:- I want to search all public posts containing #ChristmasEve
No, it is not possible anymore:
Public Post search is no longer available
Source: https://developers.facebook.com/docs/apps/changelog#v2_0
There is the Public Feed API, but:
Access to the Public Feed API is restricted to a limited set of media publishers and usage requires prior approval by Facebook. You cannot apply to use the API at this time.