Best RPG-style maps.

It is possible for a single hero of a sufficiently high level with good artifacts to defeat more than 800 devils. It is enough to have a good attack, high speed, and the Aura of Terror. However, it will be more difficult with creatures that are not affected by mind control magic, but it is still possible.

Question: is it theoretically possible to play the original 6 (or however many there are) campaigns without installing the images from the 2 discs and the clean Heroes files?

I have read this many times, but I still don't understand the meaning of these words.

Question: is it theoretically possible to play the original 6...

I assume you meant Heroes, comrade. I will say more: it is possible in practice to play as these heroes and even include them in the tavern. If you hire these heroes in the tavern (during the game), you can name them whatever you want.