Alright, I'm done! Just gonna rewrite it in details now.
Code Exotic class change;
Step 1. In dungeon 5, city 2(Difficulty **), you have to kill:
8 monsters with the wooden stick
6 monsters with the torch
The Boss.
After that, confirm the quest with the same person you started the quest and start Step 2.
Step 2. Talk to the alchemy guy in city 1 and start Step 3.
Step 3. Finish dungeon 1, city 2(Difficulty ***) and then go back to the alchemy guy in city 1 and start Step 4.
Step 4. Finish last dungeon in city 2(Difficulty **) with B rank or higher. Talk to the guy you started the whole quest to finish.
Here's the pic:
