It is mentioned in the answer to the question I linked that a person inside the cockpit can stop a person outside from opening the door by "canceling the unlock process". This leads to several further questions:
- How exactly does the person on the inside "cancel the unlock process" (Press a button, flip a switch, enter "counter code", etc...)
- It seems there is a delay before the door opens. Is this correct? What's the duration of the delay?
- What are the "authority levels" of codes? Which levels exist, what do they mean?
- What is the confidentiality policy regarding those codes in theory and practice? (Who gets what authority level code officially? If stewards/stewardesses are not allowed to have the codes do pilots usually pass them on anyways?)