Do I need multiple entry visa if travelling between HK?

Hi, I have 4 questions:
1. I want to stay in Guangzhou area for about 3 months but also want to visit HK and Macao a few times in the meantime. Do I need multiple entry to China or single entry is enough?
2. Can I apply for another entry from any country even if it is not my country? Let's say if I travel to Europe after 3 months stay there and then want to go back can I get another one from Spain?
3. Can I get a 6 months tourist multiple entry? I didn't see any restrictions on the application form.
4. The application form requires for me to state the place and contact number where I will stay. I actually intend to rent a furnished unit for 2-3 months through the real estate agency once I get there. I don't seem to be able to skip the part about the contact details. Is there any way of me just getting it without filling this part in?
Thanks
Paul