1. You have to pass the master quest on the Samurai to unlock Paladin, and on Paladin to unlock Monk and so on and so forth.
2. The more time you fail your master quests, the more starting stat points you have. On feeder, if you fail once, you get one more start stat point. On Samurai, you have to fail twice to get one stat point, and you have to fail three times to get a stat point on Paladin etc.
Let me know if you have any more questions
