About Visa Application Form

In section 2.5 of the Visa Application Form it asks to write the residences and phone numbers during your stay in China. Im travelling to China, then go to Hong Kong and then back to China again. Do I have to write and the residence in Hong Kong in section 2.5?
Also, is it necessary to have a medical insurance (section 2.7) covering your visit to apply for a visa?
Thank you.