5. You can add up to 4 images to a post (a lot of us call them toots like tooting your horn) You can set up where your thumbnails will focus. Don't forget to add accessibility text to your images. You can also post short videos and gifs.
6. In mastodon, you can put posts under a cut. We use these for content warnings, nsfw content, joke punchlines, hiding too long posts. You can also mark images as sensitive. (how these are interpreted varies a bit on other fediverse software)