Yeah, it definitely has some differences from the final version. For one thing, the game was apparently called "The House of Dead" at that point in development. Based on the text, it looks like the last scientist you save in stage 1 was supposed to give you a file or something, but in the final game she just says "Take this" without actually handing you anything. Sheds a bit of light on something that kinda confused me in the final game.
The Red Star [PS2], 2004-07-23, dumped by Where Silence Holds Sway: https://mega.nz/#!br5ghIoB!ZvQMXfy08YP6M-8-fYbdyEdCmsafw11Ik6Ei1Jpot8k
Some Mortal Kombat 3 source code and other things have been posted and then uploaded to archive.org. Apparently there's an early version of N64 MK Trilogy in there as well.
Here's some footage of the recently uncovered HOTD arcade prototype: The use of placeholder speech files lifted directly from Virtua Cop is interesting (especially as that was developed by AM2 rather than AM1), but I'm curious to know when this particular build was shown to the public, as someone in the comments seems to think it's from TGS '96, claiming that a journalist pointed out the error in its title to a Sega representative on the floor. However, I can't find any documentation to confirm such an appearance, though I remembered it being previewed the following year, and I've found evidence that it was indeed at the AOU show in '97 with its final name already in place - would there really have been presentation of such an advanced version several months earlier?
Clayfighter 2 for 32X is apparently out there. http://www.mameworld.info/ubbthreads/showflat.php?Number=379154 No ROM to be found anywhere though. Anyone got a link?
http://hiddenpalace.org/ClayFighter_2:_Judgment_Clay_(Apr_28,_1995_prototype) It's a very small proof of concept. Not sure if it even takes advantage of the 32x's hardware...
Question is if ClayFighter 2 for the 32X was further developed beyond that point or not. Interplay withdrawed from the 32X market in mid 1995 I believe, and this is an April 28, 1995 build after all. Two other Interplay titles for the 32X, Blackthorne and Star Trek: Starfleet Academy Starship Bridge Simulator, were saved from the cancellation and released in late 1995 because they were signed by Sega, which wasn't the case with this game. A puzzling aspect is that these two Sega mags from January-March 1995 unveiled what was alleged back then as "the first screenshot of their 32X conversion of ClayFighter 2", intended to be released in April. And by the looks of it, it appears to be much more developed than this late April prototype which has been around for some years and has finally been dumped and released. So, what happened here?
It's possible that the screenshot was just a mock-up or from a different version of the game (I'm not familiar with ClayFighter 2).
Turok N64's source code has also been released. I don't think there were any prototypes that went along with it though.