For more than four years, Chronoshift has been developing a project to enable fans of League of Legends to run an older version of their favorite MOBA game. Currently, the title is in the phase of closed alpha testing and takes LoL players to the end of 2010. The devs are planning to recreate Riot Games' title from its beta version to the second season (2009-2012). Most importantly, a few days ago we found out that Chronoshift's open beta tests will start at the end of next year.
For the time being, the developers do not publicly share how exactly the work on the project looks like from the inside, nor do they share the code to avoid the unpleasantness of having it copied. However, if you are curious to see how the gameplay of Chronoshift look like, one of the developers periodically uploads videos showing gameplays of different characters on his YouTube channel. Those of you who played LoL years ago can see for yourselves whether the game was properly recreated.
However, it is worth remembering that Chronoshift is a fan project and has no connection with the original devs from Riot Games. The developers point out, however, that they have obtained appropriate legal advice to make this restoration of the old LoL fully legal (although it is hard to say how much truth there is in this sentence). If you would like to take part in closed tests, all you have to do is go to the project's official Discord server and fill out the appropriate form, hoping to be accepted as a tester.