Hello!
I think the previous post's suggestion of using the ATARCalc is a pretty good one, obviously things change from year to year, but you should be able to get a good estimate of the scores you need.
Also, just one more little question. I'm the type of person that needs to understand something in order to remember it. It just feels very weird for me to sit down 5 hours a day trying to cram the information into my head. Are there any other people who are the same as I am? I need some tips in order to effectively study for year 12 since I am an inherently lazy person. I will try my best to overcome my laziness for next year as I do understand the importance of it.
You remind me of me a great deal

. This was (and is) exactly the way I feel about my studies even now (I've just finished my 2nd year of Uni). Firstly, I'll get the bad news out of the way. As much as you and I might dislike it,
there are some things you just have to memorise. There are some definitions you will have to be able to recall in your mind, whether that is for writing them down on an exam or SAC question, or thinking about the definition in order to answer more difficult questions. There are some concepts, or processes, or algorithms you will just have to know, because everything you learn follows on from the concept, and it's very difficult to answer a question without knowing the process or algorithm to follow.
Normally, people suggest to find a method of memorising things, whether that is by reading things aloud, making concept maps, putting sticky-notes up in your room, mnemonics, and a whole diverse array of wonderful techniques. But judging from your post, I sense that things are easiest to memorise for you, when they make sense. Things are easiest to memorise when you can just look back to the simple principles, apply a bit of logic, and you reach the conclusion or fact that you were trying to remember.
My suggestion would be to use your desire to understand things to your advantage. I studied mostly maths and science subjects for VCE, so most of the basic concepts that I had to memorise at least were somewhat intuitive, or fit with my general experience. There were some that were a bit more tricky to memorise - you'll just have to find a system of memorisation that works for you. Make a list of the things you need to know, and work out which items can be derived from principles. After a while, you should be getting a good idea of the things you need to memorise, and the things which you can work out through understanding and logic.
If things are easy to memorise when they make sense, then try your hardest at having them make sense! Seek explanations and derivations where possible, and see if those are easier to memorise. A lot of the time, they will be - because they apply logic from mostly intuitive first principles. Run your explanations by teachers and other students, because this will allow you to check if your understanding has gaps in it. You will still need to work at this, but at least it's a style of working that is geared towards the way you learn, which will hopefully provide some drive to do it. Over time, you will start to remember the key formula or principle anyway, simply through repeated use.
Finally, if time permits in SACs and exams, write down the key principles, or try to derive a formula if you're having some trouble remembering. I always like to start my responses with the basic principles even if they're not strictly required in answering the question, because I can develop my answer from there, applying logic as required to address the question at hand.
Be careful though, because time management is an important factor in VCE. Some derivations may take too long, or some explanations may be too lengthy to fully write under time pressure. In these situations, you may have to memorise a bit more than the basic principles (for example, memorising an intermediate step in a sequence of processes) in order to safely write down everything that you wish to, under time constraints.
However, my opinion is that it's worth taking a bit of time to make sure everything that you've written makes sense in your mind (or at least is consistent with your educated guesses or assumptions, if you haven't been able to remember everything you wanted to). To me, writing things down in a SAC or exam while constantly doubting whether what you've written is correct, is one of the surest ways to get things incorrect. Trust in your ability to logically reason. Trust in the processes that you have formed in your mind on how to get questions done. If you feel that your memory will fail before your logic does, then hone your logical skills so that you can safely rely on it when the time comes.
I hope that my perspective on memorising and understanding in VCE has helped you a bit.
Good luck, and feel free to post any questions you may have, on this or any other topic!