Look sir
here is the deal: the GRE is an exam administered in the entire world. However, it is one of the most prominent exam in UNITED STATES to get into the MBA in US, or in other programs in US, mainly for students in US.
Nonetheless, the GRE or also GMAT or LSAT are exams you need to get into a School (whatever it might be) at ACADEMIC level.
MBA, MS, PhD are all courses and programs AFTER graduation therefore advanced. Of course, it is NOT mandatory you know those nuances but they expect you should. Otherwise those exams would not exist.
Alike is for TOEFL and IELT. Wanna go in US or US contries English related go for the First one. You want to go in countries British/Australian related go for the latter.
These are the rules sir. No exceptions