Belated response, as I've finally given all episodes a try. Thanks for bringing this information out; The beta seemed to be uploaded quite a while ago.
As mentioned by others, e.g., Doom64hunter in the Duke4.net Discord or Frenkel in the PCKF, the beta has already been listed here about 10.5 years before the discovery:
https://www.betaarch...pic.php?t=30401
I don't recall enough of the game's details, but I've still went through a play-through, generally using hard skill. With one possible exception, I've managed to complete all levels.
Starting with two potential gameplay-breaking issues:
- The game with freeze upon loading E3L3 on hard skill. I've still completed the level on normal skill, using cheat codes for level skipping.
- After bringing the dialog asking if "Are you sure you want to quit?", do *not* press on N if you want to return to the game. That will abort the game, as if you were pressing on Y.
Some more bits spotted by me:
- E2L1 shows nothing for the hint globe.
- As mentioned earlier, there's an additional explosion sprite/frame from napalm bombs.
- The napalm bomb's blast does not impact soda cans the way they do in the released game.
- Over at the PCKF, K1n9_Duk3 mentioned that "the vast majority of the level files are slightly different than what's in the final release". I assume it was a data comparison. I don't recall enough from playing in the past as I wrote, but I spotted one visual tiling fix in E3L5. I think it was towards the center of the first half of the level, i.e., the half preceding the (restart) beacon.
- The restart beacons look and behave differently. In particular, once used, they'll block the way back to the area/sector preceding the beacon (they kill Duke on touch). Also, compared to the proper versions released later, there seems to be significantly reduced use of beacons in the beta, presumably for that reason.