Here is the full list of all 20 Legendary Mahjong achievements.
Get the highest rank.
Restore the Temple of Time.
Restore all the temples.
Restore the Temple of Fire.
Restore the Temple of Wisdom.
Undo 100 moves.
Use 10 Magnet Tiles.
Restore the Temple of Water.
Match 10000 tiles.
Open 10 Box Tiles.
Restore the Temple of Earth.
Restore the Temple of Air.
Match 10 Lock Tiles.
Match 10 Ice Tiles.
Restart 5 times.
Unlock the Celestial Gate.
Get a new rank.
Match the first 2 tiles.
Complete all levels in all the temples.
Use 10 Whirlwind Tiles.