Here is the full list of all 12 Forward to the Sky achievements. It takes around 1-2 hours to unlock all of the achievements on Windows.
1st Level explored
2nd Level explored
3rd Level explored
4th Level explored
5th Level explored
Sky Tower explored
Chapter 1 story revealed
Chapter 2 story revealed
Chapter 3 story revealed
Chapter 4 story revealed
Chapter 5 story revealed
Final Chapter story revealed