Instagram's live video feature is built into the existing "stories" feature -- when you swipe over to add a picture or video to your story, you'll get the option to go live instead. If you start broadcasting live video, your followers will see a little "live" badge on your story icon so they can tune in. Naturally, the interface allows for live comments to flow in, and users can "heart" your broadcast as well. Instagram is also pushing live stories into the app's "explore" tab so you can see people going live that you don't follow who might be sharing things you're interested in.
As for disappearing photos and videos, those can be sent through the Instagram Direct feature to either a single user or a group that you may be a part of. You can only send disappearing photos and videos to people who follow you, and you'll be alerted if someone takes a screenshot of your image or if they replay the video. Of course, you can draw on the images and add text, just like you can to things you post in Instagram Stories.
The disappearing messages are set to roll out today to all Instagram users, but you'll need to be patient if you want to try live video -- the company says it'll be rolling out "in the coming weeks."