What's playable here is pretty much exactly what was shown in the Rare documentary video of the game from ten years ago:

https://www.youtube.com/watch?v=w72kj20YNA0&pp=ygUNcHJvamVjd...

It strongly suggests what we have is whatever Stamper has, and that's all there was (at least in its SNES incarnation). If you do download the prototype, you can "play through" it in about 10 minutes. There's literally just the four screens.