Tech - if you have little flying experience, if you know how an engine works, parts of the plane, a bit about hong kong weather (humidity, winds, temperature, climate) you should be good to go. The more experience you have, the more they expect. If you have your ppl, expect some questions on airlaw, cruising altitudes etc.
Group exercise - be supportive of one another, build on each other ideas, ensure to keep open communication if you decide to split the work up and do not argue, but discuss. There is no limit to how many they accept from each interview group, so do not think it's dog eat dog.
Group lunch - ask questions not found on the website, that makes you look very unprepared. Find out how it's like living in hong kong as a captain, SO, etc.
Personality test - just making sure you aren't seeing ghosts or aliens. Don't over think it ahahah.
Search this thread, you'll find examples for group exercise.
Good luck and have FUN at the interview date. If you aren't having fun with your peers, you won't have fun while training ;D
Cheers,
MrJ