Jesus declared that all authority in heaven and earth was given to Him by God.
1. When did that happen?
2. Of which heaven was He speaking? The universe?
It would seem from the scripture you referenced that Christ received all power in heaven and earth at that time, when he was resurrected.
(Mat 28:18) And Jesus came and spake unto them, saying, All power is given unto me in heaven and in earth.
As the son of Man, I believe He had "emptied" Himself of His previous glory.
(Php 2:6) Who, being inherently in the form of God, deems it not pillaging to be equal with God,
(Php 2:7) nevertheless empties Himself, taking the form of a slave, coming to be in the likeness of humanity,
The heavens, refer to authority over the heavenly spiritual forces that we wrestle with.
(Eph 6:12) for it is not ours to wrestle with blood and flesh, but with the sovereignties, with the authorities, with the world-mights of this darkness, with the spiritual forces of wickedness among the celestials." ( heavens)