Hello folks. Below is a text version of the solution as well as a timestamped video for all 5 Achievements in Title Update 3.
For Secret Crystal 3, we need to play Level 7. Levels unlock as you play the game, so you'll need to get through the previous levels to get here.
Very easy. See the block to your left? Push it up two spaces and grab your hard-earned Secret Crystal 3.
Video:
Level 7 starts at 2:26