Dragonair is a Oneworld member airline and so normal Oneworld status benefits apply.
1) Yes business check in.
2) Yes Cathay/Dragonair business lounges
3) As ever, check in is with the operating airline.
[mod hat on]
These questions are specific to Dragonair, so moving the thread to the CX forum for future reference.
Kiwi Flyer
OW moderator