Hello!

I think it would be better to start from the start of the exam paper and work your way through to the end. This way, you'll know that you haven't missed any questions. Yeah, it would be a good idea to do all the easy questions first and then the more difficult questions so that you're securing those easy marks and also because it's a very time-limited exam. But, if you do that, make sure that you put an asterisk next to the questions you're skipping so that you don't accidentally put an answer for that. Otherwise, it'll muck up your whole answer sheet. You need to be really careful with this.
This method worked for me but in the end, it's up to you. Whatever works for you, you should do it. Have you done practise exams timed? And if so, what method have you been using to answer the questions?
I think the last question really depends on each sub-exam because some you might find harder and some you might find easier so you might have more or less time left depending on which one it is. Also, I think it's good to focus on answering as many questions as you can, without guessing them so towards the end, you can start guessing when you feel like you have absolutely no time at all.
I hope this helps.
