Exam questions

In year 10 what kind of GCSE revision should you be doing? Should I start doing PMT exam questions or save them for year 11?

100% start doing questions now, this will help you actually learn and memorise content that way in year 11 you can focus on topics you are really stuck on. For subjects like chemistry and biology exam papers are pretty repetitive so getting as much exam questions out of the way now will really help with mocks and your real exams! Also there is no harm in repeating questions that you have done in year 10 in year 11 because if you get them right it just proves you've learnt and if you get them wrong you then know you need to work on that particular topic.