Here is the full list of all 12 Fantastic Contraption achievements.
Beat the last tutorial level any way you can
Beat all 50 official launch levels
Win any level using 3 or fewer contraption pieces
Win any level using only wheels
Win any level using no powered wheels
Win Step then return all pieces and goal ball to the build area
Beat Tube and keep the ball in the goal for 10 seconds
Beat Giraffe then remove all pieces and goal ball from the island
Beat Log Rolling in 5 seconds
Win Stairs with 5 or fewer contraption pieces
Beat Fetch without using any powered wheels
Beat Hurl without using any powered wheels