Here is the full list of all 21 The Inner Friend achievements.
Get First Collectible
Complete the Highschool
Complete the Gallery
Complete the Hair Salon
Complete the Parking Lot
Complete the Hospital
Complete the Forest
Complete the Ruins
Complete the Mall
Complete the Cave
Complete the game
Pass the electric field without dying
Pass the Hair Salon without dying
Break all the mirrors in the Hair Salon
Complete the Simon Says section in 9 squares or less
Complete the Whack-A-Mole in one try
Let the Shadow get caught by the Beast
Beat the final room in the Highschool in 9 hits or less
Get all the Achievements
Collect 15 collectibles
Collect 27 collectibles