The resurrection of Christ was both His spirit returning to the Father, and His physical resurrection from the grave.
Luke 23:46 (KJV) And when Jesus had cried with a loud voice, he said, Father, into thy hands I commend my spirit: and having said thus, he gave up the ghost.
Ecclesiastes 12:7 (KJV) Then shall the dust return to the earth as it was: and the spirit shall return unto God who gave it.
Matthew 20:19 (KJV) And shall deliver him to the Gentiles to mock, and to scourge, and to crucify him: and the third day he shall rise again.
According to the words of Scripture after our life in this age has ended, our spirit too will return to the Father spiritually alive through Christ's Spirit in us. He will not leave us before we are physically changed to immortality. Then when this age is finished, when the spiritual Kingdom of God in heaven is complete, then believers too, like Christ, shall be bodily raised either from the grave or from this earth immortal & incorruptible. Once again whole to live with Christ forevermore on the new earth. Millennialists only imagine a period of one thousand more years of time after Christ comes again because they have no understanding of the Kingdom of God that is being built as the Gospel of Christ is proclaimed unto all the earth. Because millennials are fixated on the physical realm, they do not know of the spiritual realm being built in this age, the Kingdom of God in heaven is spiritual.
Ephesians 1:12-14 (KJV) That we should be to the praise of his glory, who first trusted in Christ. In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation: in whom also after that ye believed, ye were sealed with that holy Spirit of promise, Which is the earnest of our inheritance until the redemption of the purchased possession, unto the praise of his glory.
Since the focus of millennialists is on the physical realm, it is the only realm they know of, and that which they cannot see with physical sight they refuse to believe. You're like doubting Thomas who refused to believe without physically seeing.
John 4:48 (KJV) Then said Jesus unto him, Except ye see signs and wonders, ye will not believe.
John 20:25 (KJV) The other disciples therefore said unto him, We have seen the Lord. But he said unto them, Except I shall see in his hands the print of the nails, and put my finger into the print of the nails, and thrust my hand into his side, I will not believe.
Matthew 16:17 (KJV) And Jesus answered and said unto him, Blessed art thou, Simon Bar-jona: for flesh and blood hath not revealed it unto thee, but my Father which is in heaven.
Hebrews 11:1 (KJV) Now faith is the substance of things hoped for, the evidence of things not seen.
It is millennialists that deny or contradict the Word of God, why? Perhaps that is a question for your hearts, because it is evident that you will NEVER believe that which can only be spiritually known!
Hebrews 11:1 (KJV) Now faith is the substance of things hoped for, the evidence of things not seen.
Who said Adam was created with an immortal body? He was however created with a body that God proclaimed to be "good". It wasn't until AFTER Adam & Eve disobeyed God and listened to the voice of the serpent that sin and death through sin entered into creation. Once the physical body of Adam came under the dominion of the serpent (Satan) it became necessary that mankind MUST be born again, not of natural birth, but spiritually, through the supernatural work of Christ in us.
When man has been born again, they HAVE, not shall have, ETERNAL life through the Spirit within. That is why Christ tells us that whoever lives and believes in Him shall NEVER DIE. Our body that as you point out is not immortal, and destined to die, but our spirit, through the Spirit of Christ in us is alive forever. That's why John writes that he saw the souls (life) of saints who had physically died for keeping the faith in Christ. John did not see physical bodies that had been resurrected to life again, how could he? Since their body had expired and will not be resurrected again until the hour that is coming, when the last trumpet sounds, and time given this earth whereby man MUST be saved shall be no longer.