How to play a Unity 2.x game in Unity 5.0.1

Hello, Back when Tron Legacy came out in 2010, someone made a Space Paranoids game using Unity. The game was lots of fun and could get pretty challenging at times. However, I recently tried to revisit the game to see if it was still fun now that I am older. Unfortunately, it now tells me the following: Cannot load - 2.x games are not supported by the current Unity WebPlayer. First of all, it really irritates me that Unity wouldn't make there software backwards compatible, this seems like a huge oversight on their part. Secondly, I was wondering if there was a way to update the .unity3d file so that it was compatible with Unity 5.0.1? All I have is the downloaded .unity3d file from www.y8.com, which is a games site. If I cannot update the game, is there a place where I can download Unity 2.x.x? Or even Unity 3.x.x?