Here is the full list of all 25 Untitled Goose Game achievements. It takes around 6-8 hours to unlock all of the achievements on Windows.
Earn every other trophy
Complete the pub to-do list before the church bells ring
Complete the back gardens to-do list before the church bells ring
Complete the high street to-do list before the church bells ring
Complete the garden to-do list before the church bells ring
Dress up the bust with things from outside the back gardens
Get thrown over the fence
Catch an object as it's thrown over the fence
Steal the old man's woolen hat
Perform at the pub wearing a ribbon
Sail the toy boat under a bridge
Collect the five flowers
Make someone from outside the high street buy back their own stuff
Open an umbrella inside the TV shop
Trap the boy in the garage
Cabbage picnic
Trip the boy in the puddle
Finish the game
Complete the pub to-do list
Score a goal
Complete the back gardens to-do list
Make the shop scales go ding
Complete the high street to-do list
Complete the garden to-do list
Lock the groundskeeper out of the garden