Can a patient have two consultations with same physician for a different diagnosis in the same year?

If I understand the question, yes -- no problem. It's good medical practice to change a diagnosis if the first diagnosis is proven wrong. And if you're talking about two separate pathologies, of course that's something the same physician could concult on as well. Medically speaking, there's nothing at all special about a calendar year.

If you mean this question to relate to insurance, however, you'll have to review your policy. That said, I've never heard of a Payer limiting the number of consults for one physician, so this is probably not a problem either.