IAL further maths (edexcel)

should i give FM compound?

currently studying edexcel math and cambridge phy and CS (gonna give AS exams MJ2025)(gonna give A2 exams MJ2026)

is it possible for me to study my whole summer vacation and give AS+A2 further maths papers in ON2025?, what papers can i choose from and which ones are easy?, can i also study for SAT at the same time(or IELTS), also what are requirements for A* and requirements for A, are they same as math?

I want to do this because i will probably get bad in CS but I find math really easy so i want to make up for bad CS result with FM as fourth subject, also I think I'm pretty comfortable giving exams in october november but it might mess up my school exams for A2 which are the predicted grades you send to universities