Hello!
If anyone wants to play old releases of PB2, copy and paste this link in your URL bar:
https://github.com/eaglePB2/Plazma_Burst_2_Archive/releases
Find the "assets" of the version you want and download the .swf file.
To run the game, simply drag and drop the .swf file in a flash player projector.
Don't bother trying to connect to multiplayer because it obviously doesn't work.