Here is the full list of all 18 King's Heir: Rise to the Throne achievements. It takes around 2-3 hours to unlock all of the achievements on Windows.
Place the crown on Randall's head.
Take a moment for a tankard of liquor.
Finish a Fight Minigame without making a mistake.
Feed the animals, big and small.
Take a leap of faith into the water.
Find half of all Collectibles in the Main Story.
Finish 3 Hidden Object Puzzles without using Hint.
Finish a Hidden Object Puzzle with less than 3 mistakes.
Find the first Collectible.
Finish the first Fight Minigame without using Skip.
Finish the Lock Picking Minigame without using Skip.
Finish the final Fight Minigame without using Skip.
Find all the Collectibles in the Main Story.
Find all the Collectibles in the Bonus Chapter.
Finish a Hidden Object Puzzle in less than 20 seconds.
Finish all the Hidden Object Puzzles without using Hint.
Finish a Minigame in less than 30 seconds.
Pet all the animals, even if they run away.