Yes, I am a student at MSU
and I am happy to explain our admissions process.
We do have a "tier system". Not officially a system, but some Universities are considered better than others. This difference may be huge sometimes.
I would say any university in Moscow or Saint Petersburg is better that some main universities in provincial capitals.
We have elite Universities like Moscow State Institute of International Relations which is extremely difficult to get in. Mainly because it is an educational body for the children of our government officials and business elite. Their entry requirements are not always very clear and you do a long psychological test while applying.
We have MSU, SPSU (Saint Petersburg State University) and HSE (Higher School of Economics) which are the best three in the country and are widely known. Their entry requirements are just very high. It is relatively okay if your parents are willing to pay a huge sum of money, but if you want to get a free education in those unis, the exam results should be very high. MSU and SPSU have their own exam in addition to what all of our students do while finishing school (like A-levels probably). If you fail it, nothing can help you to get in, no matter how high are your "A-levels".
In other universities, entry requirements vary hugely on whether a student is a self/family funding or needs money from the state budget. If you go for a state budget, they may want no less that B and C, but if you pay for yourself, basically any grade will do.
Hope it helps