Travel to Guangzhou and HK

We will travel to Guangzhou in June and we would like to visit also HK.
Do we need double entry?
we need to:
- fullfil Application Form
- have a picture
- valid passport 6 months after the trip
We have booked the Hotel already. Do we need to submit booking confirmation?
Do we need anything else?
Thank you for your answers.

Best Regards,
iztok Slokar