If ATC ask for your altitude or level passing for separation purposes, what would your delay in response be?
harrowing, maybe the rules are different in Australia but here is what the UK does:-
From the UK AIP:-
The vertical position of an aircraft at, or below, any Transition Altitude will normally be expressed in terms of Altitude. The vertical position at, or above, any Transition Level will be expressed in terms of Flight Level. When descending through the Transition
Layer the vertical position will be expressed in terms of Altitude, and when climbing terms of Flight Level.
Later in 5.1.4.
Where cleared for climb to a Flight Level, vertical position will be expressed in terms of Flight Level, unless intermediate altitude reports have been specifically requested by Air Traffic Control.
5.3 Approach and Landing
On vacating the Flight Level, the pilot will change to the aerodrome QNH unless further Flight Level vacating reports have been requested by ATC, in which case, the aerodrome QNH will be set following the final Flight Level vacating report.
Altimeter Setting Procedures