Objective: Defeat 50 enemies in under 9 minutes.
Hints: I guess I won't have to tell you that's is going to be a VERY long challenge, however you won't have to worry about the time limit too much. You should be able to kill 50 monsters in about 4 minutes. You'll be going against undead creatures, so it should be a little easier to kill them. Nevertheless, avoid attacking larger groups of monsters. You will also have to use bombs and revolvers from time to time, but I'm sure that you already know all that.
Objective: Perform x40 Combo.
Hints: It's going to be more difficult to win this challenge, especially since the monsters are going to be blocking most of your attacks. As a result, you will have to make sure that you don't end your current chain by not being able to hit any new targets. Don't attack single opponents, because you might not be able to maintain a successful sequence once the monster is gone.
Objective: Collect 700 gold pieces.
Hints: This time you will be given eight minutes to collect 700 gold coins, so there's nothing you should be worried about. Like always, this is going to be the easiest challenge of all three.
Requirements: You will have to complete "Combo Challenge" for this mission.
Hints: There's not much to add here. I'm sure that you know exactly how this works - you will have to repeat the boss fight, however this time you will also have to remember about the existence of the time limit.