God is comprised of absolute truth and love. When he descends in the form of a divine incarnation he may do so anywhere, anytime, and on multiple occasions [the Bible refers to Sons of God in the plural] to show man, by example, how to live when man has lost his way. When he comes, he may come in the form of the Son of God, a servant of God, or some other disguised form.
In the current epoch, the Kali Yuga or the Dark Ages, Lord Krishna explained that good will be forced to engage in evil to defeat evil and restore righteousness. So, yes, God in his incarnate form can lie but the purpose of the lie is to restore righteousness, truth and love among his children.
There is no good without evil and no evil without good; as to know one, you must know/experience the other. It is akin to a spark that emanates from the center of the fire. God is the fire and were are the sparks made in the fire likeness and image. As the spark travels further and further from the center of the fire, it dims. This may be analogized with what you term as the devil; a lower soul who is vibrating at the lower frequency so to speak.
Crucifixion was our Lord Jesus Christ's divinely ordained mission as the Son of God. While it was within him to save himself [remember he could walk on water], he would have failed his purpose on earth if he had done so.
To learn more about all of this you must obtain a copy of "The Second Coming of Christ" by Paramahansa Yogananda. He was no ordinary person. He was here as the servant of God and once you read any of his books, I am confident that you will know that to be true for yourself.
Here is a link for his bookstore.
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It was my pleasure!