Seven Propeller Arena prototypes are now available for free download from the game's redesigned homepage. There's an alternative version (a must-try), an E3 version, a Debug Menu version and more.
I investigated it. I was able to obtain some information by talking to people who had worked on the game. I took the opportunity to write a Making-of. The 7 prototypes tell us a lot about Propeller Arena behind the scenes:https://www.sega-dreamcast-info-games-p ... t-download
The Propeller Arena prototype of April 3, 2001 is an alternative version of the game, a sort of new game inside the game (a must-try):https://www.sega-dreamcast-info-games-p ... prototype/
The June 5 Propeller Arena prototype features a Debug Menu. AM2 was still running tests:https://www.sega-dreamcast-info-games-p ... debug-iso/
The other 5 prototypes are nothing special, with the possible exception of the August 7 prototype, which features a BBA tool in the Internet options.
For Online, it was tested at SEGA of America's QA. I couldn't get any more information about it: "Yeah we tested the online feature."