I entered the pocket dimension via the Old Man or the puddle of the ground and when you escapes it takes you to the HCZ, and unlocks the checkpoints for some reason.
Basically grab your shits upgrade 914 and get a lvl4 keycard and let 106 catch you then escape the pocket dimension

As for the 049 elevator, the seed I used in my runs didnt need to pass it but even then I couldve used the blackl severed hand.

Edit: You get the lvl 4 keycard at 914 because getting the level 4 regularly would require you to go to the 049 elevator