Actual beta screenshots
There may not have been a Rescue in the earliest beta version.
A slayer in the level! Since this gun is not in the all guns cheat, we can conclude the slayer was in this level or the programmers previously allowed the slayer in all levels with the cheat.
A cyclone may also have been in the level. If you look to the far left in the picture, there is some sort of explosive object (at least I think so). And I don't see an elevator, although it could be there.