Hey there! Thank you for you kind message and sorry for seeing this just now!
In this version of the game the rats no longer need the rope, you simply need to open the pipe and they'll be able to roam freely. This change is due to me thinking it was a bit odd for them not to be able to simply jump out of it and use each other as a ladder to go back up. Same for the player, climbing there isn't that high so they could easily do so without a rope.