At the save game selection screen, select the save you wish to delete and press Start+Select on Controller 2. You will be given a Yes/No confirmation box before the save is deleted.
There are two points in the Factory in 2300 AD in which you must enter a passcode to proceed. The first point requires you to enter codes to control a crane, and the second requires you to enter the master password for the entire factory. The following lists those three such passcodes. Remember to press the buttons in order, not all at the same time.
There are 13 Endings possible in this game, depending on when you choose to fight Lavos.
After getting the Race Log to track your best scores in the bike race, race Johnny and attain a score of 777. Rx-xR will reward you with 10 Mid Ethers.
When on the black omen, you will come across a Tubster (Which at first looks like a tornado on the ground) Attack it and have Ayla use Charm, then escape, and go back through the door you came in and repeat.