I just saw the demo where he fights Shao Kahn, but Rain doesn't appear in the game. Is he a fake hidden character? Well, maybe there were still messages "Rain could be found on the Graveyard" in Kombat Kode. Finally, I found Rain's Ultimate Kombat Kode as well!! I also found Rain's moves and Noob Saibot's moves.

Rain - unlocked by Ultimate Kombat Kode (3-3-4-6-1-3-4-2-3-5)
Winner of round will fight Rain: 465-565

To play as Rain, you must be at the Subway look for a sign that says "Boon/Tobias'" look for two rains drop falling from it when you are directly under...(both start button on each side of the machine now you get to play Rain.

Rain
Spear: Back, Back, HP
Ice Clone: Down, Back, LP
Double Shadow Kick: BL, Forward, Back
Slide: Back+LP+BL+LK
Ground Ice: Down, Back, LK
Acid Rain: Forward, Forward, Down, LP
Air Throw: BL while opponent in air
Fatality #1: Forward, Forward, Down, Up (not confirmed)
Fatality #2: Hold BL, Back, forward, Up, Down (not comfirmed)
He has no babality, friendship and animality.

To Play as Noob Saibot in Ultimate Mortal Kombat WaveNet version of UMK3 arcade only. They had a hidden code to play as Noob Saibot.

Noob Saibot
Spear: Back, Back, LP
Teleport Slam: Down, Up
Slide: Back+LP+BL+LK
Air Throw: BL while opponent in air
He has no fatalities, babality, animality and friendship.

Everybody, to be honest, I tried to find play as Rain, but unforunately, it doesn't work for me at all. I couldn't perform how to find a hidden character in Ultimate Kombat Kombat and It still didn't work for UKK. I think Rain doesn't exist. I guess maybe It's not still comfirmed. I wish I can play as Rain in UMK3 arcade. I played him in MKT as well.

The question is, do you think I'm completely making it up about this?