I tested Dark Kombat and Psycho Kombat pre-patch and thought the screen was turning blue instead of black (this was when I bought the game a few weeks ago). I tested again post-patch, and it turns out either kode done in the Desert turns the screen blue while every other stage turns the screen black. Curiosity got the best of me, so I fired up my MKA Premium Edition on my PS2, and did the same thing in that version of UMK3, which leads me to believe that this particular Dark/Psycho Kombat glitch in the Desert Stage was in the original arcade version.
Unfortunately, I can confirm that the Galaga kode still does nothing. Second choice on Treasures of Shao Kahn was Random Prize pre-patch, and that is still the case post-patch (the arcade original listed that as Galaga). However, Galaga was not completely removed, as it was still accessed after 100 2-player matches pre-patch (I have yet to test this post-patch).