A levels

Hi , so i have done AS levels in Math, Literature, Accounts and Economics and am appearing for A2 for these subjects. I got straight As.
i wanted to ask about the GPA system as i want to apply in Stern. My GSCE grades were 9A* and 1A.
i read on the NYU website that a person doesn’t have to give SAT, SAT Subject tests , ACT or APs if he is an international student and has given A levels. is it true or am i mistaken?
I also wanted to ask on what basis is the GPA calculated? My school basically prepares us for board exams held by Cambridge International Examinations so its like the school is a tuition for the final exam , which is the case across the whole country. i am south asian and not from UK.
Can someone please help asap? i am thinking of ED1 In Stern… i also wanted to ask can a person apply ED2 in liberal arts if rejected by stern or there is a list of options in ED1 that if the person doesn’t get into first priority then the second can be entertained?
thanks