IDON'TGIVEUP NGL we both are kind of screwed. I'm in the same boat, now trying to try for year 10 entry for Melbourne high school and JMSS. The main thing they want to see in your application is your extra curriculars, co-curriculars and leadership roles you have done from this year and the year before. If you are a high achieving athlete (state or above) or a high skilled musician WRITE THAT DOWN ON YOUR APPLICATION. Additionally, have proof of your achievements, for example a signed written testimonies from your teachers on some activities that you did or photocopies of certificates and awards.
If you barely got anything, like me, I highly recommend trying your hardest on the personal statement segment. Try to use the schools website to your advantage, and properly express yourself for who you are and why the school should have you in the cohort, if its from your versatility, adaptiveness or wanting to be in a leadership role for that school.
Me personally I have ZERO actual curricular awards or medals, all only academic. But some of the curriculars I have written for my application were: school ambassador for secondary, assisted in community soccer events or a newly established community club, and head director for my media clubs film final for the year.
I have heard from other people that the test is actually a little bit easier this year than when we did it in year 8 and its run by EDUTEST, so do not get so worked up about it, just stay consistent in your practice test and revise on all topics, also READ books or articles. For interview questions I have been reading archived ATAR notes messages from years ago, just search "Selective school year 10 entry interview" and there would be a conversation on what usually goes on.
Sorry that I had might have gone a bit too far in my writing, If your also going for Melbourne Highschool or JMSS I hope we can see each other as classmates.