Heroes 3 (HEROECOPALKA)

But the issue with hacking the game to add specific heroes to the tavern remains :) I wonder if this hack can be detected by some program from the organizers or a sniffer? Wouldn't it be worth checking? :)

As far as I understand, you're not talking about hacking the game, but about setting up specific heroes when creating a map using the map editor.
This cannot be detected with a sniffer. It's best to simply ask the author about it.
A sniffer only scans the save file for standard cheats being read from it ;) :D :D