Was it necessary? What purpose did it serve? If humanity's sins were atoned via Jesus' death on the cross (or was it, indeed, accomplished solely on the cross?), why did God physically resurrect him? What purpose did it serve? And once resurrected, when he ascended, where did he go? "Up?" Also, we believe that Jesus has, to this day, a physical, material body. But where is it today?

Of course Jesus has a physical body. He will retain His humanity forever, along with His divinity. He returned to the Father, where He came from in the first place. His work in our behaalf isn't finished yet. There is to be a judgment. Please read the whole 7th chapter of the book of Daniel. It makes it plain, among other things, that the Father gave the Son of Man all authority. How would He exercise authority if He remained dead?