In that menu, you will find the following cheats. Once this is completed, you will gain access to the Features Cheat Menu in the Options. Having the keys, you can now remove the bars and press the switch to exit Level 32-Hectic. Directly across from you is a switch you will now be able to access. Try your best to avoid damage while getting the Yellow Key.
The floor rises in different parts of the room, and darts will fire from the faces in there. Enter the door on the left side of the room, at the opposite wall is the Yellow Key. Destroy them with your Rocket Launcher to be able to leave the room. Four Hell Knights will appear and the door you came in from will be closed. The ceiling will crush you if you stay in the alcove where you find the Blue Key. As soon as you get it, run back to the door you entered from. Enter the door on the other side of the room to get the Blue Key. Beware of the crushers that come down from the ceiling, search the wall to lower it and let it raise you back to the main room. Destroy the Arachnotrons and return to the door that leads to this room. Quickly go left or right to get the Rocket Launcher. Once you pick it up, you'll be dropped into a room with three Arachnotrons. At the beginning of Level 32-Hectic, enter the door to the right for the Red Key. To access the Hidden Cheat Menu, you must get ALL THREE KEYS on Level 32, so here is how you go about doing that. A secret area will temporarily open on the left wall that leads to Level 32-Hectic. When you reappear, destroy the barrel ahead of you on your right and enter the door behind you. Once you've destroyed all of the level's barrels, take the teleporter that you can access from the secret area behind the Blue Door. Be sure to collect the Soul Sphere and Combat Armor for a better chance at surviving later on. Remember the secret areas, the room with the exit, and the alcove in the hallway leading to the exit. Go through Level 1-The Staging Area, and destroy ALL the barrels, except the one to the right of the start. To reach Level 32-Hectic in Doom 64, you must start a new game. To get the secret Cheat Menu, you must find the hidden Level, which is Level 32-Hectic. Getting all three keys is NOT necessary to exit the level, but is needed to gain access to the Cheat Menu. In order to reach the menu, you must first discover Level 32, then survive it, and collect all three keys in it.