You don't need mana burn, but drain mana to beat them. And there is an event where you apologise to Anisa and can learn spells again.
Some areas like the school gate get characters later in the game. Others have stuff like free roam magazines if the minigames are off.
Can't speak much for the difficulty. Some find it hard, others find it easy. I think it's somewhat balanced if there are both people.
I'll think about the last one - forfeit combat. It's not a bad option to have in the Underworld.