This verse clearly establishes Christ as the God of the Old Testament. It is a false notion that there was one God of the Old Testament and another of the New Testament.
“All Eternity to All Eternity”
As we view things from our mortal perspective, it is natural to speak of things that are part of eternity past and of other things that will take place in the eternity of the future. Those past ages when all men dwelt in the presence of their Eternal Father were one eternity, and those future ages in which we hope to obtain an exaltation and to give birth to spirit children of our own and begin again the cycle of creation, redemption, and salvation constitute eternity future. Thus it will yet be said of those who obtain that exalted status, as it is of God and Christ, that they are from eternity to eternity or that they are from everlasting to everlasting (D&C 132:20).