You can watch the opening session along with livestream recordings from all 3 days of the conference. For now, the livestreams are only grouped by day. So, for example, if you want to watch a session that was streamed on day 1, you have to find which of the 3 livestreams it was part of and seek to the session you want in the video.
Epic will eventually release separate recordings of nearly all the sessions from the event, including the ones that were not livestreamed.