But aren't belief systems also a body of doctrine, myths and symbols.
So, from the meanings given, ideology refers to beliefs only intending to serve those of the social class, whereas belief systems are the opposite?
Nah the two concepts are not opposite - they are linked in a way. Like..look, a belief system is like a whole system of beliefs, whereas, an ideology is not entirely a system of beliefs followed by a certain population, but merely is like a visionary theorization, say like a set of ideas or something.
Kinda difficult to explain, but nevertheless, you need not worry coz I hereby guarantee you that there will be no question such as "Differentiate between ideology and belief system" asked in the exam.
However, if your seeking to gain beneficial knowledge as for general reasons or for a better understanding of your subject matter, I suppose you should simply ask your teacher.