I am a new student in america and this my senior (12 grade) year please help answer my questions fastwhat is the difference between the SAT and ACT?- should I take them both or just one?- which one do the colleges and universities recommend or require?-the subjects or classes students are taking this year in school, is it to prepare them for the SAT ACT or AP exam?-is the college or university i am applying to will ask for the school test scores?-ifyes,what percentage do they look at or count the SAT Score and the school test score?-if i did bad in school test scores, does this effect my applying to a college or it doesn't count?-when should i startapplying for colleges or universities?-In middle east i took SAT 2 and did Math and got 500 ,do they count it here in the colleges?-ihaven't done any volunteering yet, is it required when applying to a college? 
Please help answer the questions fast
cc.complexity theory;sat;arithmetic circuits