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