All game-related questions should be directed through the ubi.com server.

You can’t play online against AI, naturally. Heroes is a turn-based strategy game, not an RTS, so unnecessarily prolonging the game is pointless. Besides, you can play against AI on a single computer. Moreover, it’s common knowledge that the computer cheats. And at the Hero difficulty level, the player who goes to attack the AI will lose a large part of their army and then be easily defeated by the second player. I’ve never seen anyone play online against AI.
The second question is simpler. If you don’t like how the autobattle played out, just click the button to replay the battle manually. And then replay it calmly. The autobattle is always (in 98% of cases) enabled to save time on battles with hordes of zombies, skeletons, peasants, etc.