Hey man, I went to the interviews last year and I got accepted (but I turned down the offer).
The interviews are designed to see if you suit the ideals of the school and who you are as a person. If it's the same as it was last year, it won't be a typical interview throughout the whole session. The interviewers and observers, will be taking notes on how you perform under situations and during activities.
Firstly, have confidence in yourself! Trust me, if you rock a positive vibe, the people around you will pick it up and it will make you stand out from the crowd. Be friendly, make some mates on the day will help you a lot. Having some mates with you during the session will really help you feel at ease and comfortable. Your positive attitude will make a very good first impression on the people observing you. Don't go in all tensed and stressed out, go in calm and at ease. Be ready for whatever they throw at you. Just be really chill with the whole thing.
Secondly, as for questions, they're pretty general. Just have a good think about why you want to go to JMSS, how you can benefit from the school and how the school can benefit from you, your interests and ambitions, and a role model/icon of yours. They should show you the questions at the start of the 1 on 1 interview anyway.
Remember, the whole process is really about your character and if you will be an appropriate student for the school.
That's all I can say really. I wish you, and anyone else who made it past the testing, the very best of luck. If you any other questions, don't be afraid to ask.