I dont know know which guard it is. They arent numbered anymore, all of them have random space age strings of numbers and letters. One guy said the guard would be named XX-72 and there wasnt even a guard named that...
i found out abt the rock hammer hard place escape after spending 14 in game days trying to dig, find which damn mf had the key for the red door but never did, but then when i did the rock hammer escape it took me two ingame days
They updated this (or maybe it's only in the pocket edition) the door in the breaker room is accessible without chipping the wall/red key so you just need light cutters