Facebook Graph API calls -

when use /v2.4/{photo-id} in graph api explorer

it throws error : { "error": { "message": "(#803) of aliases requested not exist: {user-id}", "type": "oauthexception", "code": 803 } }

what mean ?

you seem passing {user-id} not valid data query about.

instead, use below code without {user-id}:

get /v2.4/{photo_id} 

{photo_id} id of post in userid_postid ("10000_00001") format.