John 14_20,
Is a spirit incarnate? In the Incarnation, YES
Ah.. the inclusion trick.
No no: "a spirit hath not flesh and bone". The 2 things are separate and exclusive of the other. That is why they have different names.
When Jesus said God is spirit, He Himself was both God and Man AT THAT TIME. So Jesus saying that God is Spirit does not conflict with God being human - unless Jesus was secretly confessing he wasn't really God.
So could we extend that to the fact that because Jesus was born 2000 years ago, that 1/3 of God was born then too, and that before that only 2/3 of God existed?
But rather, understand that Jesus was speaking in time, and that His statement concering the composition of God, was concerning God in eternity.
Similarly, when Elijah and Moses appeared with Jesus in the transfiguration, they appeared in their final state, yet Christ had not come to resurrect them yet.
They did not then go back to the grave, but rather, what the disciples were seeing in time, was their having been resurrected already outside of time.
When you die, you will die the same time as everybody else. For outside of time, everything is at the same 'point'. This is why Jesus said, "Before Abraham was, I am".
When God made man how long had he been unincarnate? Strange question, and quite moot. The answer is infinite, forever, unanswerable or something like that.
Not as strange as your answer. Until you answer it, you are in default.
Now, put that together with James 1:17 as you have requested (God does not change) and you are obviously looking for a conclusion that states that God must still be spirit.
Well if that verse leads you to think that this might be the conclusion, then what does that tell you about your theology?
Here's another for you: when Christ appeared physically to Abraham before Sodom, was he incarnate?
But if God was Spirit, and He cannot change, and He is still Spirit, then He never could have become man.
He can become man in the time realm. And He created time inside of Himself.