In order to reenter "Fragile Existence" (level 9), you have to satisfy two conditions:
- the cursor must be on top of the level (in this case Baba)
- the cursor must not be on top of another map element, e.g. another level or the path
At first, this seems like an impossible condition. However, the cursor can move on-top of Baba off the path. Or to use game terms:
CURSOR ON BABA AND NOT ON PATH IS ENTER.
CURSOR ON BABA IS WALKABLE
So in order to play the level, you have to move Baba to the cursor and then move away from the path. The easiest way is to go into level 8 ("Slideshow") and then back to the map. Afterwards, move down, right and then left: