Here is the full list of all 43 The Lost Legends of Redwall™: The Scout Act 3 achievements.
Finish the Winsome Wraith
Answer every Stoat Riddle correctly
Slingshot all destructibles in Winsome Wraith
Collect everything and complete all objectives in Winsome Wraith
Shimmy all the way around the chandelier
Finish Portman's Slough
Get a Perfect Score on Mila's Dialog Game
Slingshot all desctructibles in Portman's Slough
Collect everything and complete all objectives in Portman's Slough
Sink every island in Portman's Slough
Visit Lyra's grave in Portman's Slough
View Fog, Fog, and More Fog in Portman's Slough
Finish Grating Gulley
Convince Jeb to make up with his brother
Convince Jeb to stay mad at his brother
Slingshot all destructibles in Grating Gulley
Collect everything and complete all objectives in Grating Gulley
Find all five traces of Bolo's passage
Complete Grating Gulley without using a reset
Finish Fool of a Stoat
Get a perfect score on Cheesethief's dialog game
Slingshot all destructibles in Fool of a Stoat
Collect everything and complete all objectives in Fool of a Stoat
Listen to the rats' entire song
Finish The Otters' Den
Complete The Otters' Den without dying
Slingshot all destructibles in The Otters' Den
Collect everything and complete all objectives in The Otters' Den
Find the Gloomer's skeleton in The Otters' Den
Interact with Scumsnout's corpse
Finish Cavern Hole
Talk to all 34 critters (including unlockable characters) in Cavern Hole in one sitting
Slingshot all destructibles in Cavern Hole
Collect everything and complete all objectives in Cavern Hole
Present the completed memoir to Pickerel
Find the Act 3 Talisman
Learn all Scents
Unlock all Character Biographies
Fully upgrade the slingshot
Fully upgrade the hat
Collect 25% of all Jam
Collect 50% of all Jam
Collect 100% of all Jam