Consider the following premises. r_4 <-> q_2. ~r_4. r_2 -> q_2. Can we infer r_2 from them?
 From r_4 <-> q_2 we can infer q_2 -> r_4. From r_2 -> q_2, q_2 -> r_4 we can infer r_2 -> r_4. Finally, from r_2 -> r_4, ~r_4 we can infer ~r_2, which contradicts r_2. Therefore, the answer is no.