This trick will exploit a fatal error when applying the "+set developer 1 +set sv_cheats 1" command line parameter, if you get the "You cannot cheat on the server" message. After starting the game with that command line parameter, start a new game. Set the level and start it. Then, save the game and exit the game. Restart the game and select "Resume". Do not manually select a game to load. Just "Resume" your current game.