In the sentence above "are interviewed" is correct.
You asked if it's ok to have two verbs in one sentence. Yes. Your sentence is really in two parts (called clauses): "All the applicants are interviewed" and "a final decision is made by the authority". The parts are joined by the word "before" which tells us how the two actions are connected.
We use two verbs in lots of sentences when we use connecting words e.g. and, because, after, when, who, while... the list is endless.