Achievement "The Golden Child" - Earn Gold Prizes on all Hard difficulty stages
Guides and videos for all stages can be found on the Catherine Wiki:http://catherinethegame.wikia.com/wiki/Walkthrough:Overview
Hard mode is quite frustrating: You have less time, NO UNDO, you don't get a bonus at the end of a stage. So basically you have to try for perfect runs and get most of the gold coins (you do not need all of them, most important is the combo bar).
My tip: Do the final stages first and work your way through the stages backwards. Then the worst is over first. Especially Level 9 ist VERY frustrating because of all the random things which can happen. Monster blocks moving in your way, bad luck with random blocks, bad luck with bossattacks, monsters in your way...
Even with the great videoguides you'll have a hard time. Good luck.