Cheat mode enabling:
To enable cheat mode in a game you should start it (ALONE4.EXE) with 'wizardmaster' or 'WIZARDMASTER' (no quotes) option in command line. Then when you enter the inventory, you will see the cheat menu there.

Infinite Saves:
As Carnby, when you leave the lobby of the manor, a cut scene begins and you meet Edenshaw. At the end of the cut scene he gives you a charm of saving. If you save immediately after the cut scene ends, then reload, the cut scene will begin again. Repeat. You will gain 4 saves each time.