The Insights section for Facebook Groups is more limited than for Facebook Pages. We can’t get insights for Group’s posts. All information provided for now will be Members count and Member waiting for approval.
For each group’s posts are displayed the comments and reactions. The class for Facebook Groups can be customized to provide more information.
Is possible to create new comments and reply to comments, but the api don’t allows to delete posts or comments. Another problem is in publishing of comments. You can see in the video below the posts is possible to publish, but Midrub there is a problem, and comments creation will be disabled until the begin of the next month.