Easy and Hard difficulty:
To unlock Easy difficulty, beat the game in less than three hours or beat the game on Hard difficulty. To unlock Hard difficulty, beat the game on Normal difficulty.
Easy money:
In the market, there is an orange can. Kick the can behind the counter of the Jet Bakery. A message will appear and say you have received 1,000 Zenny. Leave the room, then return and the can will reappear. Repeat this trick as much as possible to get an unlimited amount of money. Note: Later in the game the amount will be increased to 2,000 Zenny.