Here is the full list of all 21 Just Find It 3 achievements.
Find 10 Difference.
Find 50 Difference.
Finish 10 Difference Mode Levels.
Finish 30 Difference Mode Levels.
Complete All Difference Mode.
Complete All Swap Mode Levels.
Complete All Match Mode Levels.
Complete All Detail Mode Levels.
Complete All Montage Mode Levels.
Complete All Cycle Mode Levels.
Complete All Memory Mode Levels.
Use Hint for the first time.
Use Hint at least 10 times.
Use Hint 30 times.
Play a Difference Mode without using Hint.
Play a Swap Mode without using Hint.
Play a Match Mode without using Hint.
Play a Detail Mode without using Hint.
Play a Montage Mode without using Hint.
Play a Cycle Mode without using Hint.
Play a Memory Mode without using Hint.