Here is the full list of all 24 htoL#NiQ: The Firefly Diary achievements.
You have cleared Chapter 2
Completed the maze area in Stage 2-2 without dying, and within 60 seconds of stepping on the switch
Died 10 times
You have cleared Chapter 1
Touched the toxic waste in Stage 1-2
You have cleared Chapter 3
You have cleared Chapter 4
You have completed the game
Cleared Chapter 1 and defeated the boss without dying at any point
Cleared Chapter 2 and defeated the boss using no more than 3 boxes of explosives
Cleared Chapter 3 and defeated the boss without letting it regenerate at all
Answered every question correctly during the Chapter 4 boss fight
Collected every Memory Fragment
Cleared Stage 1-1 in under 80 seconds without dying
Cleared Stage 1-3 after collecting all the stuffed animals
Cleared Stage 2-1 without dying, and without using the levers more than 4 times
Completed the maze in Stage 2-3 with Lumen within 2 minutes and 10 seconds, and without touching the sides
Completed the floating portion of Stage 3-1 without landing once
Gazed at the moon in Stage 3-2
Fed the Shadow Bird seeds in Stage 3-3
Cleared Stage 4-1 without dying, and without opening the doors more than 18 times
Cleared Stage 4-2 and defeated every shadow enemy in the elevator area
Cleared Stage 4-3 after passing through all the pipes
Died 100 times