Wow, that's it! But I still think that I played a leaked prototype of that game, because it didn't have any other details like the vegetation, and the rotating cube didn't transform into the game's title. Great to see they actually finished it! lol
So, Metal Mutant (1990-1991) came before Flashback and Legend of Kyrandia (both 1992). I can't recall a previous game that has such impressive artwork. It seems they modified the gradient from blue-orange (sky-desert reflections) to colors that match the environments, which makes it kind of monochromatic. So the prototype looked even better as I recall.
https://archive.org/details/msdos_Metal_Mutant_1991