When He came as the Angel of the Lord in the OT, was not Jesus there, correct?Is God the Son, Jesus?
No one is arguing against that; what is being argued is that the efficacious nature of Christ extends outside of time. This is exactly why the cited passage in Revelation states. Was Christ the lamb, slain before the foundation of the world?
Well, in the compound sense, yes. In the divided, no. This is where you are failing to make the biblical distinction.