What's different? Well, the game's story mode apparently has only two playable main characters, as opposed to the five available in the final game. One of those leads is Serena Corsair, while the other is, strangely enough, a white-clad version of Valgar Reinhart. He isn't playable in the final version's story mode, though he has a prominent role as the standard semi-honorable bad guy who turns halfway good once the real villains are unmasked.
And now, an early version of Alien Soldier, Treasure's blisteringly hard Mega Drive action-shooter. These shots come from the May 1994 Gamefan, back when the title had a Slab Bulkhead human hero instead of the bird-headed cyborg seen in the final.
For comparison, here's a shot of the released game's main character and one of the bosses seen above.
And here are huge scans of those Alien Soldier and Guardian Heroes previews. The shots of Alien Soldier are lumped in with early Light Crusader screens, but I never liked that one enough to compare it now. Even my Treasure fetish has limits.