I plan to leave Metropark Hotel in Shenzhen direct to HKIA to catch up my flight 9:00 Pm out of HK.

From your hotel, there is no such bus service. You are suggested walk to Shaibu Station to take the Longgang Line. Get off at Shopping Park Station. Take the EXIT D and walk about 0.4 miles to the Futian Shangri-la Hotel, where you can take direct bus to the HK airport.
The travel time is about 2 – 2.5 hours.