First things, open days aren't until August. That's also the same month when VTAC (uni applications) open.
In terms of your subjects, you'll be fine with English. Just read your texts.
For Chemistry, this will be the hardest to do if you don't know much stuff from Unit 1/2.
Make sure to go over the mole concept, look at concentrations, stoichiometric calculations, gas laws and revise writing equations. Basically go over all the maths involved in Unit 1/2. That's all we did for my year 12 orientation last year. If you understand that stuff you should be fine with everything else. Oh you could go over some organic chem. Would be very useful.
Further you should be able to pick it up easily. I have no clue with Bio as I didn't do it.
Methods, best to go over functions and relations, and the sketching involved with it. Also if you're weak on trig, then definately go over that. Also if you've never done them before, try to teach yourself Matrices.
Good luck with the transition. Feel free to message me or ask anyone on the forum for help