There is God the Father of the Old Testament and there is God the Son.
As for God the Father:
Deuteronomy 6:4
Hear, O Israel: The LORD our God is one LORD.
The one LORD & GOD mentioned in God the Son:
Old Testament God Is New Testament Jesus
Genesis 1:1 God is the Creator
John 1:3-10 Jesus is the Creator
Genesis 17:1 The Almighty is God
Rev. 1:8 Jesus is the Almighty
Exodus 3:14 The “I am” is God
John 8:58 Jesus is the “I am”
Deut. 10:17 The Lord of Lords is God
Rev. 19:16 Jesus is Lord of Lords
Ps 18:31 The Rock is God
I Cor 10:4 Jesus is the Rock
Psalms 22:16 They pierced my hands and my feet
Zechariah 12:10 They pierced me – God
John 19:34 They pierced Jesus
Ps 146:10 God shall reign forever
Luke 1:33 Jesus will reign forever
Isa 40:11 The Shepherd is God
John 10:16 Jesus is the Shepherd
Isa 41:14 The Redeemer is God
Luke 1:68 Jesus is the Redeemer
Isa 43:10 God said, “I am he”
John 8:24 Jesus said, “I am he”
Isa 43:10,11 (God is the Saviour
Luke 2:11 Jesus is the Saviour
Jer 31:32 God, the One Husband
II Cor. 11:2 Jesus-The One Husband
Zec 14:4-5 God is coming
Matt 25:31 Jesus is coming
Mal 1:6 The One Master is God
Matt 23:8 Jesus is the One Master
Isa 43:15 The Holy One is God
Acts 3:14 Jesus is the Holy One
Isa 43:15 God is King of Israel
Matt 27:37 Jesus is King of Israel
Isa 45:21 The One Saviour is God
Acts 4:12 Jesus is the One Saviour
Isa 43:10,11 God is the only Saviour
Titus 1:4 Jesus is the only Saviour
Isa 44:6 The first and last is God
Rev. 1:8, 22:13 Jesus is first and last
Isa. 44:6 The King of Israel is God
John 1:49 Jesus is King of Israel
Isa. 45:23 Every knee must bow to God
Phil 2:10-11 Every knee must bow to Jesus
Psalms 22:16 They pierced my hands and my feet
Zechariah 12:10 They pierced me – God
John 19:34 They pierced Jesus
The ALMIGHTY GOD throughout the OT is:
Jesus Say's here: Rev 1:8 I am Alpha and Omega, the beginning and the ending, saith the Lord, which is, and which was, and which is to come, the Almighty.
2 Timothy 3:16 (A)
All scripture
is given by inspiration of God,