All great questions. The openings for this garment are in the back and are metal snaps. Here is a picture of the back openings:
For diaper changes, you would undo the snaps that run along the top of the bottom and pull their legs out, so you wouldn't have to completely undress the baby.
The sleeve length is long sleeve. As far as washing the garment, the care label states to machine wash warm and tumble dry medium. We do only ship orders Monday thru Friday.