Aviates 01,
Just put n/a (not applicable) in the HK correspondence address, that way the HR staff will know to respond to your home address instead. The form is probably a leftover from the days when cadet recruitment was for local permanent HK residents, or for candidates that have family members living in HK.
With regards to your your contact number, if you plan to keep using your US sim card whilst you're in HK then you need to do it in the following format:
+1 (USA dialling code, not +852 as this is HK's number) your 3 digit number + 7 digit number.
Good luck with Stage 2!