Qiyas and Tahsili in English **PLEASE REPLY**

I'm a Saudi and  studying in an International School British Curriculum. Though I'm worried about these exams.. I want to take them in English though my concern is that I think the exams are based on the American Curriculum, correct me if I'm wrong. Do you think it will affect that I'm studying British and its in American? How can I prepare for these exams? Is there like a check list of all the topics I need to know for each subject?  And can you tell me the difference between the two exams? Also for the English section I just want to confirm but will I have to write with the American spelling ? Also how will they test me on English? Will they just ask me about grammar and sentence structure? Also for Math's will they tell me to show my working out? It would be a GREAT help if you could answer all my questions :) Thank you.