Final Fantasy VII Cheats
Once the player comes into contact with the fourth Huge Materia on the Rocket, they end up in space. While in space, the player must input a passcode for the Huge Materia in order to obtain it.
The correct code is Circle, Square, X, X. However, even if this isn't obtained the rocket still collides with Meteor and is unsuccessful.
Obtaining Bahamut ZERO
If Cloud has obtained both Bahamut and Neo Bahamut during the course of the game, by examining the blue Huge Materia in Bugenhagen's observatory, he can receive the Bahamut ZERO materia, which is an extremely powerful version of the Bahamut Summon.
Taken from the following website, which is a fantastic visual guide and resource Link