I believe the west elevator of stratum 3 takes you to the north-east of stratum 1.
the blue switch must be pressed in stratum 1 and teleport traps are active. there is a teleport trap near the north east elevator that transports you near seconda.
You also need to spam your movement skill (space, w) to move fast enough.
Finally moved 3 rooms away and go back.
(Written again in case it translates badly)
1) press blue switch in stratum 1
2) take tentacles to stratum 3 western elevator and use it.
3) step into nearby teleport trap.
4) run to seconda lab while avoiding traps
5) spam movement skill while doing this.
6) leave, walk a few rooms away and return to seconda
