In UAE, all security checking agents are locals only. They do not allow expatriates to hold those positions due to security issues.
Key to the cockpit invasion is the relationship between captain Robin Allen and a stewardess. It is presented as a regular extra marital affair taking advantage of layovers in Dubai (or other long haul destinations for Kingdom Airlines). But commercial airlines crews are not colleagues just travelling to the same destinations, the roster hardly allows for the chance of the captain to work with the same copilot and cabin crew member during one given year.
When the aircraft is on the gate it receives the takeoff clearance from ATC. At this stage an aircraft will never receive a takeoff clearance, as before that it has to contact ground or delivery to receive the information clearance, and after that the push and start clearance. Take off clearance is provided by tower control, normally when reaching the runway holding point, or even when lined up on the runway.
Young girl finds a bullet in lavatory, hands it to an older gentleman and you can not only see that it's been fired, but it's also clearly a blank round, i.e. no projectile.