Here is the full list of all 26 Inbetween Land achievements. It takes around 2-3 hours to unlock all of the achievements on Windows.
Earn all the achievements
Watch all game cutscenes
Complete the whole game without using a hint
Start the island's motor
Complete the blocks minigame without skipping
Complete all minigames without skipping
Bring all the crystals back to the Main Hall
Make the solvent
Complete the microscope minigame without skipping
Create a new flask in the oven
Open the doors in the tower corridor
Open the looters' safe
Fix the music box in the library
Feed the pet in the library basement
Illuminate the library basement
Complete the numbered door minigame without skipping
Complete the associations minigame without skipping
Complete the books minigame without skipping
Complete the tag minigame without skipping
Retrieve the crystal from the lake with the robot's help
Complete the combinations minigame without skipping
Visit the lake with the robot
Learn about the island from Mary
Open the well hatch in the utility room
Get to the island through the portal
Give the toy back to the dog