Of course you can hop off the aircraft, in fact it's likely you will have a different one anyway for your next journey. As a J customer you have a plethora of lounges to enjoy:
G16 Lounge
Location details: Airside, Level 7, entrance near gate 16 at Level 6
Opening hours: Daily: 06:00-mid night
Business CentreFree WifiFood and BeveragesWheelchair Access
Qantas International Business Lounge
Location details: Airside, Level 5 (entrance via Level 6 opposite Gate 15)
Opening hours: 05:00-23:59
Business CentreFree WifiFood and BeveragesShowersWheelchair AccessTV
The Cabin
Location details: Airside, Level 5, entrance near gate 23 at Level 6
Opening hours: Daily: 05:30-last departure
Business CentreFree WifiFood and BeveragesWheelchair AccessTV
The Pier Business Class Lounge
Location details: Airside, Level 5, entrance near gates 62-66 at Level 6
Opening hours: Daily: 06:00-2330
Business CentreFree WifiFood and BeveragesShowersWheelchair AccessTV
The Wing Business Class Lounge
Location details: Airside, Level 6 & 7, reception near gates 1-4 at Level 6
Opening hours: Daily: 05:30-last departure
Notes: The Wing Business Class lounge has re-opened with a new look after the completion of a head-to-toe renovation. The new space features brand-new facilities – The Noodle Bar, The Long Bar, The Coffee Loft, Self-served buffet and 24 luxurious shower suites.
Business CentreFree WifiFood and BeveragesShowersWheelchair AccessTV
If you are also transiting on return via HKG, note you cannot buy Duty Free liquids to take back to Australia airside, it needs to in your checked baggage, so either buy it at the destination on arrival or get bags checked to HKG only and buy it on arrival, then recheck bags, having said that HKG is not the best as far as pricing goes but better than on arrival home.