All routes take some chance, here is the quickest/least rng involved.
Start on level 0, wander until level 1 > do the "double back"* to get to the hub > Take the hub** to level 11 > noclip the ground to get to level 153 > find the neon wall (whatever that is) > take the wall to level 3999 and walk through the door. make sure you were a good noodle before.
(entrances and exits)*
(there might be a door to level 3999 in the hub)**
Was this too convoluted? it was pretty safe. There are not many ways back into the frontrooms. Theoretically, you could just noclip back the way you came, but it would take someone magic to do this...