Hi din
I did the mghs entrance exam for year 10 entry this year and its honestly alot better than the year 8 acer test. The maths content doesn't go in too deep the questions relatively easy just practice time. There is literally no breathing time with 60 ques 30 min. The edutests practice help so much because they are similar to the actual test. Try the year 9 - 11 ones don't be intimidated by the grade. Be consistent with studying, program as much vocab into your brain. If your not sure of a word during the test try breaking down to it' prefixes and roughly make an educated guess based off it's etymology, you don't need to be fluent in latin.
Don't be stressed on the day and listen to every instruction given to you by the instructors. I saw some kid next to me give up during the test but don't let that slow you down. I myself am not to sure of the interview process as I am still waiting for the dates for mine (wish me luck!) but just be confident and show off your achievements with out bragging. Sign up for those curriculars cause they asked for our school reports before the offers came out, the reports are one of the key steps of getting your interview.
Best of luck to you!