Summary: the word of God is truth. No lie is of the truth. The NKJV contains lies. Therefore, the NKJV is not of God.
A book may say "Bible" on the cover, but that does not mean that it is the word of God.
The word of God versus the NKJV
The word of God is truth. No lie is of the truth.
The New King James version of the bible (NKJV) has lies in it. And no lie is of the truth.
Therefore, the NKJV is not of God. It follows that the NKJV is a counterfeit.
Example of a lie in the NKJV
Compare Exodus 34:14 with Galatians 5:19-20 in the NKJV:
You see that the NKJV on one hand confirms in Exodus 34:14 that God is a jealous God, while erroneously claiming that jealousies are sin in Galatians 5:19-20, thereby implicating that God is a sinner. And that is a lie.
The King James bible
The word of God is found in the King James bible (KJV). In the KJV, Galatians 5:21 mentions "envyings" as a sin, which indeed is sin. If you love truth, get a King James bible.