I finally completed the Optimal campaign. Whew, the beginning was very difficult. I spent a whole month just developing the hero.

And after capturing the northeastern Castle, everything becomes easy. The hero becomes strong and capable of independently defeating many neutral creatures. In short, everything is easy from then on.
I have three questions about the scenario:
1) Why is the level limited to 20? If there are no other visible limitations...

2) When I was freeing the Crusaders in the north, west of the shooting range, I was told that this was the first step and that I now need to capture Castles, even though I had already taken two "Castles"... obviously, it's a script, but the question is, how can I break through 40 ghosts and almost 40 imps (there were about that many imps) with a handful of archers, a weak hero, and 2 Crusaders? Is that even possible?

3) I wasn't allowed to enter the city of angels through the quest gates, even though I had an angel in my army, taken from the pyramid, even two angels (the quest says that there must be angels in the army. What did I do wrong?
P.S. I took the angels first, and then went to the gates.

It's a pity that the final hero is VERY weak. Without an army and with parameters that are the same as my Optimal hero, or even less, considering that I also had 2 angels, 8 champions, and 30 Crusaders.
But for the difficult beginning, a big "+")