Why Studying Model Theory is important to Philosophy? How much Math and Logic one needs to know to get down to study Model Theory? and does it have something to say about Hierarchical essence of scientific language?
I'm not sure studying model theory is important to philosophy, broadly speaking. For some areas, such as the philosophy of set theory, it surely is important that one know at least something about the basic results and techniques, since they are used regularly in set theory itself. But I doubt one really needs to know very much model theory to work in philosophy of mathematics generally. (I don't, and I do.) A general understanding of how what models are and how they are used in studying logical consequence is probably adequate, which means, roughly: What you'd get in any good sequence of logic courses. Of course, if you want to work in logic itself, then how much model theory you need to know will depend upon which branch of logic interests you.