If i have valid China Visit Visa , do i still need to take visit visa for HK

I have Pakistan Passport and UAE Resident , following are my questions
1- I have valid China Visa and will be travelling to Shenzhen , after finishing my trip i intend to visit HK for 3-4 days , do i need a visa?
2- If my return flight to Dubai is from HK , do i still need to get HK visa as i heared i can take ferry from Shenzhen and go directly to HK Airport