Catherine

To get the Let My Sheep Go achievement you have to complete all 3 stages of Stage 3 The Torture Chamber. This chapter introduces trap blocks which are a pain. Here are some links to some great video guides that will help.

3-1

http://catherinethegame.wikia.com/wiki/Walkthrough:Torture_C...

3-2

http://catherinethegame.wikia.com/wiki/Walkthrough:Torture_C...

3-3

http://catherinethegame.wikia.com/wiki/Walkthrough:Torture_C...

These links show how to achieve gold on every difficult. I hope this helps.

Stage 3 is the Torture Chamber; it has three levels and introduces trap blocks. If you want a proper walkthrough, go here for videos:
3-1: http://catherinethegame.wikia.com/wiki/Walkthrough:Torture_C...
3-2: http://catherinethegame.wikia.com/wiki/Walkthrough:Torture_C...
3-3: http://catherinethegame.wikia.com/wiki/Walkthrough:Torture_C...

If you'd rather get through the levels yourself, here's some information on trap blocks:
Trap blocks are easy to spot; you can see the spikes through the side. You'll want to walk/jump onto the block and immediately off of it. This will trigger the trap and the spikes will then break and the block will be safe to walk on. You can simply run straight across the trap, run onto it and jump up/down a block, or even run onto it and hang off its edge, and you will be safe. If you try to pull a block onto an armed trap block, or push/pull a block while standing on one, you will die.
TL;DR Trigger and disarm trap blocks by walking onto them and immediately getting out of the way.