I expect the only way would be to install the appropriate version of Quake 3 to play the demo. I believe if you copy the pak files and executable somewhere else, you can swap them in to play that version again.
you can download a program called seismovision from planetquake3.net ... good program for watching demos including old versions etc..you can just double click the file from any location on your pc
this demo should have x.dm_66 so u can simply rename it into x.dm_67 and select it in the demos-folder in your game-menu. but i would also select seismovision, its much more practical :)
fat looks horrible in this demo, even for him it's just such a strange total lack of awareness, thinking, strategy. Maybe Zero4 was so far ahead on pro-t4 and his rail so good that he scared fat into playing that way, but man, even I would try to use rl and rail a bit more. Fat just kept running at him and trying to stream plasma like a freaking ghostbuster. ZeRo4 is no ghost, bloke.