Discussion of mapmaking works!

Message from OptiMAL
Everything is done using a trigger.
Regarding the monster: it's better to place events X cells before the monster so that it doesn't attack, and create a trigger for when the neutral changes ownership. Otherwise, I don't think it's possible)
Regarding the hero: If there is a trigger, then it can be done.

Yes, I'm already doing it with a trigger; I just wanted to clarify if there was another way. I tried again with a hero—the neutral switches to another flag, but the hero owned by the player does not switch. That's a pity. I'll have to find another way.

Message from Смерть Попсы
3. Remember that your level must be at least 20 upon completion of the game

Not only does the hero start without an army, but they also need to be given level 20. This will be problematic even on L, unless you flood them with experience while completing the quest.