Hi - not sure if this might be useful, but I found it really helpful to tailor my questions to the person I was asking! For example, I always asked grad recruitment what fictional character the firm in question might be, because it allowed me to get a perspective on how they viewed the firm and also what the firm was trying to highlight about itself. (According to grad recruitment Freshfields is Cinderella and Stephenson Harwood is dead set on being Sherlock Holmes, if you happen to be interested in Disney or classic detective novels) 😂
Obviously, sort of question might come across as little frivolous in an associate/partner Q&A!
I usually asked about key challenges that they had overcome during their careers, reasons they had transferred to (or trained at) the firm, or even long-term challenges that they thought my intake of trainees would have to overcome. I ended up getting some fantastic answers about changes in international client-bases, difficulties with NQ retention, and challenges with client-communication that the partners were facing in their daily work. Your interview time with a partner is really valuable to improving yourself as a candidate- these sorts of answers really helped me get a pulse on how the legal industry is shifting and gave me a better idea of what I might face as a trainee.
(If you're feeling exceptionally bold near the end of a one-to-one interview, you can ask the ultimate useful question- whether the partner thinks you personally would fit into/contribute to the firm, but this might be out of place if the interview style isn't particularly casual/conversational.)
Also, in my own experience of a large group Q&A exercise, really clever-sounding technical questions (ie. questions about percentage shifts in interest rates, LIBOR etc.) tended to come across as slightly out of place and over-studied, so unless you have a specific reason for wanting to know something technical I would avoid that sort of thing.
Best of luck on your AC- I'm sure you'll be brilliant!
