There isn’t a level select, all of the described achievements are missable and listed in chronological order. The rest of the achievements are storyline. You’ll need to play through the game 2 times for each difficulty, I suggest collecting everything on Explorator mode while leaving the Shadow master for the Survivor mode since it can only unlock there.
Explorator mode
Chapter 1
This is hardly a missable as it can be at any point by just AFKing in the shadows for a minute.
Shadowbathing
Stayed in the shadow for a minute straight
This is another easy achievement to get at any time, I don’t suggest doing this during your Shadow master run.
Deadly sunburn
Stayed in the sun for too long
Climb up the stairs to get the candy
Sweet miracle
Get the chocolate candy
At the blue van, turn left, on top of the red barrel, pick up the inhaler.
Plastic relic
Get the inhaler
During the night breaks between chapter 1-2 and chapter 2-3, go to the front of the truck to show your Mom one of your collectibles.
Mom, look!
You showed your mom something you found
Chapter 2
Inside the green tent, pick up the magazine.
Archive from the past
Get the magazine
Inside the white tent, pick up the weird plushie.
Weird fluffy thing
Get the weird plush
When chasing the dog inside the warehouse, turn a corner to find the toilet paper in the shopping cart
Golden roll
Get the toilet paper
You’ll soon find the dog, from now on you can pet him 5 times with “E” and throw the ball with “Space”.
Who’s a good boy?
Pet the dog
Who’s a REALLY good boy?!
Pet the dog 5 times
Fetch!
Play with the dog
Climb up on the shelf from the right, pick up the puck.
A memory of dad
Get the puck
Chapter 3
Hard to miss, pick up the chalk before going down the ladder.
Colorful dryness
Get the chalk
You’ll now have all the collectibles.
Hoarder
Get all collectibles
Survivor mode
This isn’t a hard achievement, take your time to move between shadows and it’s easily doable. This achievement only unlocks on the Survivor mode.
Shadow master
Complete the game without dying