Below are the instructions on how to get this working, these instructions were taken from Fabian's instructions from Project Nemo, remember, this must be done on the japanese version of Ace Combat 3 (Disc 1):
-Music Player: Works just like the Music Player that appears in the AppenDisc. You can play any track that appears in the game and a few "unused" ones including The Execution, for some reason the track Defiled does not appear in the track list although it is present in Disc 1.
Note: While the Music Player lists all the tracks used in the game, it skips the ones that aren't present in the current disc.
Movie Player: Really, really incomplete, almost non-functional, you can only play the introductory movie that appears when you start a new game.
Model Display: Works like the Model Display featured in Ace Combat 2, you can select almost any aircraft that appears in the game exception the UI-4052 and the UI-4053. The Model Selection screen is just like the Aircraft Selection screen that appears before starting a mission in the story mode.
-Directional Pad/Left Analog Stick: Rotates the aircraft
-L1: Zoom In
-R1: Zoom Out
-Extra Menu: Accessing Method
1 - Boot the game
2 - Create a New Account using the default name (Nemo)
3 - Set the difficulty to Hard
4 - Leave all the other settings unmodified
5 - Save the account in the Memory Card Slot 1, in any "sub-slot".
6 - Watch/Skip all cutscenes/dialogue/etc.
7 - In the Pre-Mission Menu, select Options
8 - Once you are there, activate the following Gameshark codes:
The "Extra" menu should appear inmediately.
Highlight any option of the menu and deactivate the codes (If you don't deactivate them you'll be stuck in the Extra Menu since the codes force the game to load that menu)
- Extra Menu: Known Glitches
If you use the Music Player after using the Model Display some of the graphics of the time counter will be corrupted, that is because when you enter to the Model Display the game replaces the graphics used by the Music Player with the textures of the aircraft currently displayed but it doesn't retrieve the original graphics after you leave the menu.
If you try to use the Movie Player after using the Music Player the game will freeze.
Some emulators may crash while attempting to load the Movie Player.
The Model Display is very unstable, if you scroll too fast in the aircraft selection screen you may end up freezing the game, although maybe that's just an emulator thing."
Remember, while navigating on the model viewer don't go too fast while switching planes, this may also cause the game to crash.
ALL credits for discovering this goes to Fabian from "Project Nemo" (http://useatoday.blogspot.com.br/2014/04/ac3-hidden-extra-bonus-options-menu.html)
Credits for recording all this footage goes to my friend RythusOmega: