We don't breathe with our arms, legs or eyes. We breathe with our lungs. And not "developing" lungs either; fully-formed lungs.It grows, it draws nourishment from it's mother it starts developing and forming arms, legs, eyes etc.
If you're just talking about oxygen exchange at a cellular level, all cells do that.
I've seen photos. Enough to realize that your anthromorphic descriptions of embryos don't fit with a morula or blastocyst, i.e. stages when the embryo is literally a microscopic ball of cells.Have you ever seen an embryo?
Unfertilized eggs grow, change and are viable.I know you directed this to someone else but I have the rational basis of seeing the development of different stages of growth in different embryos. I believe based on my observation that an embryo is a living, viable form, if not there would be no growth no change, the embryo would not be viable....