Consider the following premises. U_1(a_12) <-> R_4(a_12). forall y: R_4(y) <-> U_1(y). Can we infer R_4(a_12) <-> U_1(a_12) from them? If possible, name the inference rules being used at each step.
We can infer R_4(a_12) <-> U_1(a_12) via the universal instantiation rule. Therefore, the answer is yes.