[Pbdz]

Si, diciamo che sono necessari entrambi i requisiti...

Ho provato a creare un post tramite graph explorer e ottengo questo:

{
  "error": {
    "message": "(#200) If posting to a group, requires app being installed in the group, and \
          either publish_to_groups permission with user token, or both pages_read_engagement \
          and pages_manage_posts permission with page token; If posting to a page, \
          requires both pages_read_engagement and pages_manage_posts as an admin with \
          sufficient administrative permission",
    "type": "OAuthException",
    "code": 200,
    "fbtrace_id": "Al0IPFLqGaYKnN4e0lNDohr"
  }
}

Credo che l'app debba essere installata dall'amministratore del gruppo