Delete Forum Thread via REST - Does it remove replies and images

In version 8.5 (or 10.1) if I use the REST API to remove old forum threads will that:

1) Also remove all of the replies to those threads?

These forums have been used as a Classified Ads feature. Users post to the forums via email with pictures of their items attached to the email. The images are not put into a media gallery. They are retained as part of the post.

2) Will the images also be removed or will they be orphaned?