To get the list of questions from a SP 2013+ Distribution list using OOTB REST API:
_api/lists/getByTitle(‘listname‘)/items?$filter=ContentType eq ‘Discussion’
or
/_api/lists/getByTitle(‘listname‘)/items?$filter=FSObjType eq 1
To get the list of replies from a SP 2013+ Distribution list, using OOTB REST API:
_api/lists/getByTitle(‘listname‘)/items?$filter=ContentType eq ‘Message’
or
/_api/lists/getByTitle(‘listname‘)/items?$filter=FSObjType eq 0
To get the list of Discussions with the replies count from a SP 2013+ Distribution list, using OOTB REST API:
/_api/lists/getByTitle(‘listname‘)/items?$select=ID,Title,Body,Folder/ItemCount &$expand=Folder/ItemCount &$filter=ContentType eq ‘Discussion’
