A full beta version with many differences and unique maps. Note that it's broken out-of-the-box. You need to supply missing files from version 222 and the patch. To make music work, go to Advanced Settings → Audio → enable UseDigitalMusic and restart.
This version "requires" 3dfx card to run. But nowadays nobody has such cards. To unlock the game just put a file called glide2x.dll in C:\Windows\system32. It can be even empty zero bytes file. You can also install some glide wrapper and have additionally hardware accelerated graphics.