Consider the following premises. forall y: ~T_3(y). forall y: T_3(y) <-> U(y). forall y: Q_3(y) -> U(y). exists y: T_3(y) -> U(y). Can we infer forall y: T_3(y) <-> U(y) from them?
That is one of the premises. Therefore, the answer is yes.