"I know that God is not a partial God, neither a changeable being; but he is unchangeable from all eternity to all eternity" (Moroni 8:18).
Two questions:
In your oun words, what does this verse mean?
If god is "unchangeable from all eternity to all eternity" how can he change?
An excellent question.
If you are a Christian, you undoubtedly believe (as I do) that Jesus Christ was and is God and therefore unchangeable.
Nevertheless, Jesus clearly changed. He was born as a baby and grew to manhood. During that time, "Jesus increased in wisdom and stature, and in favor with God and man." (Luke 2:52) Eventually, he suffered death on the cross, rose again the third day, and ascended into heaven.
Hence, Jesus Christ is an unchangeable being who changed. How do we resolve this apparent contradiction?
I believe that the key is the doctrine that God is love (1 John 4:16). Jesus has always been perfect in his love for God the Father and for his fellow men. Likewise, he has always been perfect in faith, hope, mercy, and justice. Although he was "in all points tempted like as we are, yet [he was] without sin." (Hebrews 4:10). In short, he has always been completely good.
Jesus Christ changed physically, but the Godly attributes of his character do not change.