You don't need to know the 74 inside out unless that is your current equipment. They will ask questions about what you currently fly, but they wont quiz you on an aircraft you don't fly or are rated on.
You should know just basic information on the Cathay fleet (it shows interest in the company). Details like type of engines, having a general familiarity with the powerplant's charachteristics (RR is 3-spool), that kind of information. Don't go memorizing the minute details of the aircraft. There is more important stuff to know in HTBJ. Know the concepts in that book well enough to discuss them in a realworld scenario. That is way more important than knowing how many rivets are on the 74's stabilizer.
Good luck on the interview.