Resident Evil: Director's Cut Codes and Unlockables (PSX)

An updated version of Resident Evil for the PlayStation, titled Resident Evil: Director's Cut, was released in September 1997, 18 months after the original release. Director's Cut was produced to compensate for the delay of the sequel, Resident Evil 2, and was originally bundled with a playable demo of that game. The main addition is the inclusion of an 'Arranged' mode featuring new camera angles, different item and enemy placement, a more powerful handgun and new default outfits for Chris and Jill (as well as Rebecca). The original game is included as well, with a new "Beginner" setting where the amount of ammunition uncovered by the player is doubled.

A second release of Director's Cut (known as the Dual Shock Version) was released in Japan and North America. The Dual Shock Version featured support for the Dual Shock controller's analog controls and vibration functions, as well as a new Gothic soundtrack by Mamoru Samuragouchi, replacing the original soundtrack by Masami Ueda. The Japanese version of the Dual Shock Version came packaged with a bonus disc that contained downloadable save data and footage of the Japanese dubbed version of Resident Evil and gameplay footage of Resident Evil 1.5 (the canceled version of Resident Evil 2).

Codes
Highlight Advanced Mode at the main menu, then press and hold Right until the word Advanced turns green - Double Ammo

On the difficulty select menu highlight Advanced and hold Right for a few seconds - Easier Advanced Mode

At the demo title screen highlight New Game and hold Right for a few seconds - More skill levels

Unlockables
Beat the game on any mode with Chris or Jill in less than 3:00 - Unlimited Rocket Launcher

Complete the game in Advanced mode and save all your partners - Unlimited Magnum

Complete the game once in Training or Standard mode with either character and save all your partners - New Costumes

Glitches

Infinite Magnum Ammo in Advanced Mode
When you place the red jewel into the tiger statue, three cases of magnum ammo will be revealed for the taking. Take one (or two), leave the room, and then enter it again. All three cases will have respawned. Use this as many times as you like for infinite ammo.

Here's an extremely useful playthrough video with Chris: