I thought there was a way to make map for sc1 anti-cheat where you could only play it on multiplayer not in single player mode. You could still play it with one player only, but it didnt allow you to use cheat codes forcing you to play in multiplayer games.

You could just have a trigger that does the Pause Game action, which does nothing in multiplayer.
You could also use EUDs to check for multiplayer.

single player camera centers contain a wait action, multiplayer camera center actions do not do that... -> detect that this wait occurs... you can do that via setting a switch, center camera, and reset the switch again... then have a trigger that stops the game when the switch is enabled.
multiplayer -> trigger won't run... singleplayer -> trigger will run