Add '-cheatenable' into command line of the game (mgsi.exe -cheatenable)
 and use the following keys in game:

 Key             Effect
 ------------------------------------------------------------------------
 [F2]            God mode. Please be patient about this mode ability to
                 switch off, so if you see life amount decreasing just
                 press [F2] again.
 [F4]            Sometimes (I haven't idea about this undeterministic
                 work) makes infinite ammo.
 [F5]            Normal view mode. Useful after F6 (see later) effect.
 [F6]            Observe mode. Seems the camera places into the center of
                 the level and you can navigate it. Use [F5] to turn back
                 to normal mode.
 [F7]            Fast level restart (NOT reload!). You will be placed at
                 level start but will have all that you have before key
                 press.
 [F8/F9/F11/F12] Some sort of texturing modes switching. Just experiment
                 with this key by yourself.

 By -= CyberMan =-, cyberman@ag.ru