How to Unlock the Dev Room
How does one access the dev room?
A few steps.
If you go the netrunner shop to pick up the hack that T-Bug says that you should have, you will be in the right area. Go downstairs to where the gun shop is;
and turn right and keep going until you see a garage door on the end.
At this point, you will have a keypad next to the door. The code is 605185.
After entering this code, you will have unlocked the door.
P.S. Doing this later on in the story is advisable.