This is the only truly missable achievement in the game
. You unlock 21/24 achievements automatically during your 'regular' playthrough, and 2/24 during your 0% playthrough.
You will need to do this during your main playthrough of the game, which will require you to place 7 "god" cubes and sprout their respective trees. After placing the 7th and final god cube (Rainbow) you will see the Rainbow Tree sprout. Make a save
(just incase). Now, you will need to back track to the map/mandala room, the location of which is in the above video I made (a visual reference is much easier than a text/descriptive one). It's not a difficult path at all, but due to the infinite symmetric Escher-esque nature of this game it can become disorientating quickly. Enter, select any map to return to a previous level, and you will earn this achievement.Note: For this achievement you do need to return to the final map room in the game. There is one after every god cube technically, but I believe you need all god cubes to be able to actually be able fast travel between them. If you aren't getting the option to select a level when you find a map room, this is likely why.