Here is the full list of all 26 Children of Silentown achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Collect the "Trumpet" sticker.
Collect the "Lucky charm" sticker.
Collect the "Egghead Lucy" sticker.
Collect the "Hairball" sticker.
Collect the "Spyglass" sticker.
Collect the "Mysterious footprints" sticker.
Collect the "Broken toy" sticker.
Collect the "Coal's fur" sticker.
Collect the "Complicated padlock" sticker.
Collect the "Big metal ruler" sticker.
Collect the "Blue's drawing" sticker.
Collect the "Old kettle" sticker.
Collect the "Glass shards" sticker.
Collect the "Doll" sticker.
Collect the "Windmill" sticker.
Get the cat as best friend.
Collect the "Puppy" sticker.
Collect the "Depths of the well" sticker.
Collect the "Huge Snail" sticker.
Collect the "Flower of hope" sticker.
Collect the "Mysterious paintings" sticker.
Get one of the children as best friend.
Choose the Children's Song.
Choose the Mom's Song.
Choose the Song of the Forest.
Choose the Song of the World.