Downloading is possible for both photos and videos from posts, as well as for stories, reels or profile picture.
All returned resources are determined by the Instagram API and also depend on whether the user has enabled the Media API in the script settings.
Script is a very good idea. I hope you continue developing it and there are more users and more donations.
But how to increase Highlight/reel screenshot jpg quality (of still frame mp4)? Currently it seems it only generates 71% jpeg files with 2x2 subsampling which is kind of low quality.