Not actually, but it is not identical to nonexistence. It's capacity. If something didn't first have the potential for something, it could never become actual in that manner. And which potentials something has depends on the kind of thing it is. Thus, only human beings in their early stages have the potential to be adult human beings.

You're basically committing the error of Parmenides all over again.

No, it is literally identical to nonexistence. An acorn is not an oak tree. If I were looking for objects that satisfied the properties of having a trunk and providing shade, an acorn would not qualify.

On an arbitrarily large timescale, many things have the potential to become other things. Depending on your preferred theory of abiogenesis, some frothy chemical soup on early Earth had the potential to become, and did become, all of life. This does not give the soup moral value equivalent to all of life. What matters is what things are now, not the other things they could turn into.