God never attained/achieved immortality. He has always been immortal.
1st Timothy 1:17 states, "Now unto the King eternal, immortal, invisible, the only wise God, be honor and Glory forever and ever. Amen."
Psalm 90:2 - "Before the mountains were brought forth, or ever thou hast formed the earth and the world, even from everlasting to everlasting, Thou Art God.
The Lord is the Living God who never dies. He lives forever and forever. He is the Eternal king. His rule is Everlasting and his kingdom is eternal. As stated in Daniel 4:34, Daniel 6:26, 1st Timothy 1:17, Revelation 4:9, Revelation 11:15, and revelation 15:7.
