Outer Limits 4x4 Board

hey guys, i am new to 4x4ing so hopefully someone could help with my question. Today in an argument at work, i was told that the handbrake is located behind the gearbox, so we jacked one side of the diff and we couldnt turn the tyre in the air, when then jacked the other side and the same thing happened. So we then decided to jack one side of the diff again and push the car off the jack, the car rolled forward and thencar came off the jack but the tailshaft didnt spin at all? So we then jacked both rear wheels off the ground with the handbrake on and both wheels spun in the same direction. My 2 questions are, 1- is there somthing wrong with handbrake/diff & 2-if my car is in a rut with one tyre in the air, would my handbrake hold it or will it roll forward? Someone please help.

handbrake is on the gearbox.

one wheel up, handbrake on. wheel wont spin if you turn the wheel in the air

one wheel up, handbrake off, in neutral, tailshaft will spin if you turn the wheel in the air

both wheels up, handbrake on, wheels should spin opposite but against the lsd

both wheels up, handbrake off, wheels will spin in the same direction

if you have your hubs locked in and in 4wd with one wheel up you shouldn't roll too far becuase the HB works through all four wheels.

handbrake is on the gearbox slash tailshaft'
should the car roll forward in this situation?

assuming that the vehicle has a rear locker or tight LSD, if the handbrake is fitted on the tailshaft and is on, neither rear wheel should turn, regardless of whether one or both wheels are in the air or on the ground and doesn't matter whether or not the transmisson is in gear... at least that is my understanding.

Just a note though, just caus the handbrake is on, doesn't mean the 4wd can't slide on a slippery slope, best bet is to have it in gear and in 4wd with the hubs locked with the handbrake on.