Since Jesus is God, He did not *come into existence*. He simply existed from eternity past, with the Father and the Spirit. Had He created absolutely nothing, it would have made no difference. He is the Self-Existent I AM (with the Father and the Holy Spirit).
So at the incarnation of Christ, the Holy Spirit supernaturally brought about a miraculous conception within the virgin's womb, and the child which was conceived was Jesus. But He had already existed before time began as "the Word of God", the Creator.
As to the temptations of Christ, since He was born of a virgin, He did not have a sin nature inherited from Adam. Which means that He was sinless and could not be tempted to sin. That is because God cannot be tempted to sin, neither does He tempt any man.
Satan is not omniscient, and he foolishly imagined that he could present temptations to Christ and have Him succumb to them. But he could not know that the Son of God cannot be tempted.
It is only when people forget that Jesus is fully God and fully sinless Man at one and the same time (not comprehensible to humans) that we have all kinds of heresies about the Person of Christ.
KJV Romans 8
2 For the law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death.
3 For what the law could not do, in that it was weak through the flesh, God sending his own Son in the likeness of sinful flesh, and for sin, condemned sin in the flesh:
4 That the righteousness of the law might be fulfilled in us, who walk not after the flesh, but after the Spirit.
5 For they that are after the flesh do mind the things of the flesh; but they that are after the Spirit the things of the Spirit.
6 For to be carnally minded is death; but to be spiritually minded is life and peace.
The Son of God became fully human, taking on the flesh of
fallen man.
KJV Hebrews 2
18 For in that he himself hath suffered being tempted, he is able to succour them that are tempted.
KJV Hebrews 4
15 For we have not an high priest which cannot be touched with the feeling of our infirmities; but was in all points tempted like as we are, yet without sin.
16 Let us therefore come boldly unto the throne of grace, that we may obtain mercy, and find grace to help in time of need.
No trace of Imperfection in Christ—Those who claim that it was not possible for Christ to sin, cannot believe that He really took upon Himself human nature. But was not Christ actually tempted, not only by Satan in the wilderness, but all through His life, from childhood to manhood? In all points He was tempted as we are, and because He successfully resisted temptation under every form, He gave man the perfect example, and through the ample provision Christ has made, we may become partakers of the divine nature, having escaped the corruption which is in the world through lust.
The obedience of Christ to His Father was the same obedience that is required of man. Man cannot overcome Satan’s temptations without divine power to combine with his instrumentality. So with Jesus Christ; He could lay hold of divine power. He came not to our world to give the obedience of a lesser God to a greater, but as a man to obey God’s holy law, and in this way He is our example. The Lord Jesus came to our world, not to reveal what a God could do, but what a man could do, through faith in God’s power to help in every emergency. Man is, through faith, to be a partaker in the divine nature, and to overcome every temptation wherewith he is beset.
If Christ did not come in our fallen human nature, then He had an advantage over us that we can not emulate... He cannot then be our example.
The fact that Christ could have sinned in His humanity, is greater evidence of the incredible risk the Father took in giving His Son to the human race.