His body.
Correct. He committed His Spirit to the Father. Jesus is the Spirit of God who took on a human form.
That is not a traditional Christianity belief. Some fringe religions may, but it's not a Christian teaching.
The Spirit of Christ, like our spirits do not die. Our bodies die. Our spirits return to God.
Very picturesque language being written there. It is not literal of course.
His body died, just like ours does. They laid Him in the tomb, just like we are laid in a grave. His Spirit was with God, just as our spirits are with God when we die. The difference is, that because Jesus is God, He could and did raise Himself from the dead. It is mystery that no man can explain. Sometimes, as much as we want to get it all worked out with our human minds, we cannot and it was never intended for us to do so. That is where faith comes in. Belief that what God did is the truth.
The Bible describes death.
. 4 For whoever is joined with all the living, there is hope; surely a live dog is better than a dead lion. 5 For the living know they will die; but the dead do not know anything, nor have they any longer a reward, for their memory is forgotten. 6 Indeed their love, their hate and their zeal have already perished, Eccl 9
With all of Jesus' activities he does not fit the definition of "DEAD"