In China - you should only use your Chinese passport, and yes many of those who have foreign passports will hide that when entering China, but the legal status is that China do not recognize dual citizenship. In HK, technically that rule also applies, but turn a blind eye until now because so many hkers have BNO passport (British), Australian and Canadian - but they will NOT recognize them unless you complete a "Change of nationality declaration" - which I have done, you will still be considered as a Chinese national in HK, hence NO consular assistance in HK!
https://www.smartraveller.gov.au/destinations/asia/hong-kong - Nationality information
- Chinese law doesn't recognise dual nationality. The Australian Government may be unable to help if you enter Hong Kong on a travel document other than your Australian passport or if you're deemed a Chinese citizen. If you're travelling from Hong Kong to Macau or mainland China, use your Australian passport.
- If Hong Kong authorities consider you a citizen of China, they may refuse access to Australian consular services.
https://www.immd.gov.hk/eng/services/chinese_nationality/Change_of_Nationality.html - Change of nationality forms