Prerequisite can be used as both a noun and an adjective, requirement is a noun.
What do you choose:
Being able to drive is one of the ....... of the job of salesman.
A-prerequirements
B-prerequisites
C-prescriptions
And the answer is B. I don't know exactly why they choose it :(
There are few to no "differences" between synonyms.
They are words with equivalent meanings.