I am curious on what you unlock at the end of Resident Evil 3: Nemesis. Once I beat the game in under 6 hours, I unlocked a New Mode and a key with two outfits. What are those and how to I use/play them?
If this is your first time beating the game, you can start a new game and you'll get the Boutique Key in your inventory, which can be used to unlock the Boutique in Jack's Street
There you can change your outfits.
About the new mode unlocked, it's probably Mercenaries, which can be accessed by loading the save file you created when you beat the game. In the load game menu you'll see NEXT GAME, load it and it'll show an option to start a new game or go to Mercenaries Mode.