Application questions-US Citizen with HK ID card and Mainland Travel Permit for Hong Kong Resident

Thank you so much in advance! I am a US citizen with US passport, and I have a HK Permanent ID Card, and Home Return Permit (回鄉咭) but it has expired. My child was born in US.
1. Can my child apply for 10-year visa if his passport is only good for 5 year?
2. My son traveled to Hong Kong and Taiwan a few months ago. When answering #7.4, Hong Kong and Taiwan was not an option. How should I answer it?
3. For myself, I was born in HK. How do I answer # 1.6C whether I hold other nationality? Because HK is not an option and if China is selected, it says I cannot apply for a visa.
4. Under # 1.6G, I have to answer Yes for former nationality. Selecting China will ask me to provide former Chinese ID number and last Chinese passport, which I have never had. I only have HK ID card and Home Return Permit. How do I answer the question?
5. For # 5.5A, my spouse was also born in HK. But HK is not an option under Country. Can I select Unknown and enter Hong Kong under City of Birth?
6. I have been to China before using Home Return Permit. But it has expired. Do I need to provide this information anywhere?
Any comment is very much appreciated!