Hey,
Sounds like school has been pretty shit so far. How have you teachers been treating you recently? Do you know which teachers you have next year? If you do, are they teachers you dislike? I get what you mean that's pretty much how I felt for years 7 and 8, luckily I was able to move schools.
Firstly, whilst there may be people who claim to do extremely well without trying, it is simply not true. Most of the time people claim this because they either want to appear smart or they don't want to be embarrassed at working hard, but then not having results that reflect that. My issue with talking about how hard people work is that the response can go two ways. It is either 'oh you don't study much you must be smart' or 'you study lots, i'm not doing enough', and the truth is neither of these are true. One person might seem not to study much, because they don't study after school, hen in fact they spend most of their before school/lunch time/ whenever else studying instead. Or someone says 'i spent all this week studying for that SAC' but then someone beats them who didn't spend the whole week studying. But perhaps person 1 didn't study at all the month before, and person 2 did. You just don't know. This is why I avoid talking about how much I study, just because it takes me a certain amount of time to learn something does not mean it will take someone else the same length of time. Whilst I understand this is really frustrating, I don't really have any advice other than to ignore them, and know that there is more going on than what they are telling you.
If you don't feel like your teachers are helping you this year, feel free to ask any questions you have in the relevant sections on here instead, and someone will get back to you. You said that you can't complete the specialist activities you have been set, so how about you post one of them in the spec forum and someone will show you how to go about it. For English, you can post your English essays and someone will give you feedback on them to help you improve.
If you have some sort of chaplain/school counsellor/etc you can talk to them about this, and they have to take your side
They will know your situation better than we do, so they can give you some more practical advice. It also sounds like the bullying from the past is still affecting your confidence, so it may help to speak to someone about it - If you don't want to talk in person there are anonymous phone numbers you can call, there are also online resources available eg. Youth beyondblue, reach out, black dog institute, kids helpline, all have some great resources for teenagers.
Don't worry too much about your atar at this point, there are always pathways to get into the area you want to study. If you know the general direction you're heading in I'm sure I can find some of them for you to have a look through, although it is far, far off at this point, it can be reassuring to know that it will all turn out okay
VCE is just a few years of your life, you still have another 60-80 after you graduate.
Adding to what Sam M said, don't feel like you have to drop any of your subjects if you don't want to. I did 3/4 psychology, 1/2 English, 1/2 biology in year 10. I also did 1/2 methods for the first half of the year and failed it epicly (I got 14% for one test - I picked B for all the multi choice), definitely not a math person haha, but if that's your thing, go for it.
Definitely don't feel like you have to know what you want to do in the future. For now just keep doing subjects that you enjoy and you can't go wrong. I still don't know (although i've mostly decided on a uni course, beyond that is unknown). I had absolutely no idea until i did a fish elective in year 10 and realised that fish were cool. I then did 3/4 bio this year and realised that bio is cool, so i'm going for something to do with enviro science or medical research areas. I would advise trying out new things to get an idea, you might find something you enjoy, also maybe sit down one day and go through random uni courses and copy any that look interesting into a word document - chances are you will notice a theme.
Sorry for the super clunky reply, I had trouble sorting what I wanted to say into an organised reply, let me know if anything doesn't make sense.