First: I think every question has a logical answer. is it correct?
Second: If the answer to my first question is yes, then what is the logical answer to the question why a cow has four legs?
If by "a logical answer" you mean an answer that is logically consistent , then I agree that every well-posed question has a logical answer. Nevertheless, the logically consistent answer to some question will often rely on information from beyond the subject matter of logic. The answer to why a particular cow has four legs will rely on information about the cow's parentage, genetics, embryology, anatomy, or some such. Logic all by itself cannot answer that question.