There is an alternative version of the 23rd titled "23 Beta - Open the Missing Link", where Okabe fails to save Kurisu in which would eventually lead into the story of Steins;Gate 0, the upcoming sequel. The beginning is pretty much the same as the original. Only the last 7 or so minutes are altered. This also includes a preview for Steins;Gate 0 at the very end of the episode which shows Amadeus Kurisu, an AI version of Kurisu. Check the wiki for more details.