You say that the New Testament era doesn’t really begin at Jesus’ birth. You say Jesus was born “under law” and that the New Testament era began at Jesus’ death. What evidence is there for your view?
But when the time had fully come, God sent His Son, born of a woman, born under law, to redeem those under law, that we might receive the full rights of sons.
Galatians 4:4-5
In the case of a will, it is necessary to prove the death of the one who made it, because a will [testament/covenant] is in force only when somebody has died; it never takes effect while the one who made it is living…
Hebrews 9:16