7th Interportal Tournament of HMM3-OFF: "Earth Magic"

How do you actually use codes so that the game doesn't complain later? I tried to test it once – I loaded a clean game, entered the code, immediately killed the process, loaded the same game again, finished it – and it said "cheater." (Just finished a map – it was interesting, I liked it), and the result for the day was worse than the calculated minimum, but you can't even send such a save for the campaign. I tried running a second copy of the game in a virtual machine, which helped, but copying saves dozens of times was incredibly tedious.