Consider the following premises. p_4 <-> q_3. ~q_4. p_4 <-> q_4. Can we infer q_3 from them?
 From p_4 <-> q_4, ~q_4 we can infer ~p_4. Finally, from p_4 <-> q_3, ~p_4 we can infer ~q_3, which contradicts q_3. Therefore, the answer is no.