Hello! I take only some of the subjects your taking ( chemistry, biology, maths, english, language (chinese) )
My best advice for science subjects and maths would be to do past papers, if you don't understand a question or didn't get it right, go search online, like on YouTube or ask a friend or teacher for advice or explanation to knowledge you don't understand. You won't learn if you don't ask questions!! That is reality. If you really don't have a clue and can't find the exact answer or explanation right for you to understand (that's okay, because everyone take in information differently) go and ask ChatGPT.
For English, write out the texts you need to know and first test yourself to see how much you can analyse and explain in detail and write them down. It is a good idea to create a mindmap for this. Go onto Youtube or notes your teacher has given you and see how they have analyse it. By the way, there is going to different interpretations, and so, if you have your own opinions and thoughts on analysis, try talking to your teacher and see if it is valid and if they agree with it. Often enough, you will understand better by analysing it yourself and having your own interpretations of it.
For languages, it is recommended to listen to the language more. There are so many beginner friendly videos on YouTube that you can just listen to in your free time. Slowly, you may be able to pick some up and you can use it in writing. Also, create some kind of vocabulary, grammer and sentence structure lists and stick them on your wall or somewhere where you will frequently pass it. Try to spend time every day, even if it is 10 minutes every morning before breakfast, to look at it and try test yourself on them. Trust me, it is very useful (especially for people who aren't native speakers).
To answer you question on mock exams, your school has no reason to make an assessment that has nothing to do with the content you have learnt. So my first advice is to fully understand the course specification, that is the bible to the examiner when they are making the exam. Secondly advice, again, would be to do past paper. You will slowly be able to figure out the exam board's way of asking and creating questions.
And, don't worry if you don't know how to make a revision timetable or revision. These things can be found on the internet, for example, go onto 'Pinterest' and search up 'study revision timetable'. You will get loads of ideas and inspirations on how to make them. There are so many ways to revise- you must find the best way for you to revise, and trust me, that is one of the most difficult things to do as a student. For me, I am a person who learns by diagrams and by hearing . I also have my own whiteboard. Over the years, i have found that I am really good at teaching myself by using the whiteboard and doing active recall (trying to force out information without notes), especially for biology. I also use the blurting out method.
I hope this helps in any way and good luck! This journey is tough but very fulfilling.
I wish you all the best in meeting your targets ❤️