hi how can we go to emperor wan chai hotel from hk airport via airport express train? thank you

Well, you can take airport express to HK Station first. It will take around 24 mins on the way. Then walk to the Central Station and take Island Line to Wan Chai Station, Exit B1. After arriving, walk to the destination.
Or you can take bus no. E11 at Airport (Ground Transportation Centre), and get off at Luard Road, Hennessy Road. After arriving, walk to the hotel directly. It will take around 70 mins on the way. And the ticket fare is 21 HKID.

can we use airport shuttle bus so that we dan reach the hotel faster? thnk you

The first answer shows the AE train and airport shuttle bus choices. In comparison, AE train + MTR takes less time.

where to buy octopus card for tourist? how much? is there a deposit? any refund applicable for unused amount? How about the deposit?

Well, you can take the airport express to HK station. After arrival, take the free shuttle H2 and get off at HK Convention and Exhibition Center. After then, walk to the southwest to reach the hotel.