I can't beat the "Croatia" map.

So, it's WoG. That's what I thought. When the map was created, WoG probably didn't exist yet, and that wasn't the author's intention. He's just a lazy one.

The original version 3.0, unfortunately, didn't launch.

Well, if you managed to launch WoG, you can try launching it from the same folder using Heroes3.exe: that's the original version. By the way, it's good that you wrote in this thread: I was just remembering this map the other day (I didn't remember the name) as a prime example of why it's necessary to test maps. I started writing an extended chapter about testing maps, returning to the guide for beginner mapmakers. I think I'll post it later.