As you know, some cheats in Half Life v1.1.1.0 dont work(for some reason) I noticed I should type "sv_cheats 1" before starting a game. But in Source, its all different. Explaination? Also, if yours is working fine, please share it.
It is sv_cheats 1. then you type god notarget noclip etc.. Noclip doesn't work on HL1 until you've passed through a loading point on the original HL though.