How To Access Facebook Groups Information Through Facebook Graph API

Intention —

Access a closed group's (whom I'm admin of) posts and comments without providing facebook functionality.

Confusion —

First -

developers.facebook.com/docs/graph-api/ref… and stackoverflow.com/questions/30830210/faceb… says that user_managed_groups permission is needed to access the information of a group of which.

developers.facebook.com/docs/graph-api/ref… says that one needs to submit the app which intends to use user_managed_groups permission. But how to use a dummy closed group for testing purposes without submitting?

Second -

Can I make access group's information (posts and their comments) without having a Facebook login functionality ?