Hello there.
I have 25 years corporate R&D experience using C and C++; and teach C++ to engineers worldwide.
I also conduct workshops in C++ and can have recently completed a C++ Q&A for a client on this portal.
Based on your budget range , 500 questions ( advanced C related questions, their answers and explanations ) is NOT going to happen- unless I use questions from the internet.
If I were to do this properly, where I formulate each question my self, and give you the answers and surrounding explanations.. it would take many many days to complete, but would be an expert level offering, and hence the need for a more respectable budget.