At Main Gate with all items & key items, buster parts, special weapons upgraded to the max, max health upgrade, max zenny, and play time is 1 hour so that easy and hard mode will be unlocked after beating the final boss. 

Save file that starts the game off at the very beginning in hard mode without having to beat the game first. Normally, you'd have to first beat the game and then the option for hard mode is shown on the main menu temporarily. It isn't a permanent unlock like the N64 version, so it's a pain to access it