Gonna PokƩpost here because I'm not sure where else to, but hear me out.
A thing that I consider with Mewtwo and Mew is that while Mewtwo is man-made, Mew isn't. Mew carries the ancestral DNA for all PokƩmon. Mew, much like Ditto, is an amalgamation of cells. Mew can use any move and use transform and all sorts of things like that. Mew is not limited by Mankinds hubris, so to speak. But Mewtwo is.
Despite being a clone of Mew, the fact of the matter is that there were still gaps in the DNA sample that the scientists retrieved. In PokƩmon Special, we even learn that Blaine used some of his own DNA to fill those gaps, so Mewtwo contains some Human DNA. So it is limited by that in both body and mind. Because of this, Mewtwo cannot learn every move like Mew can, etcetera etcetera.
That being said, I think Mew, because of it's ability to change its form and learn every move, has the ability to regenerate itself, or alter its own cells into liquids, solids and gasses at will. I don't think Mew is a pokemon that can, for example, die of old age or natural causes. Mew doesn't need to rest, eat, refresh, or anything like that (except in battle, but that's just gameplay for you), but because Mewtwo is so limited by it's physical form, it DOES need to eat and rest and so on and so forth. And it isn't happy about it, either. Power comes with a cost.
I see it like Jurassic Park. The DNA extracted from the Mew fossil was incomplete. They had to fill in the gaps with Human DNA (or Alakazam DNA, depending on what theory you subscribe to) and by doing that, Mewtwo became flawed. Both sets of DNA have merged. The Human cells are not malleable in the same way the Mew cells are. Mewtwo cannot transform because the human cells are incompatible. Mewtwo therein cannot learn every move, and requires rest and food much like any average PokƩmon would.
He has the powers of a god but the physical limitations of a mortal. And there's nothing it can do about that.
That being said of course, while in the cloning machine, Mewtwo didn't need to eat as it was likely absorbing nutrients through its skin or eating through a tube or something similar. It didn't need to rest as it was in a comatose state. I'm certain during its training with Giovanni it had to eat food and sleep, and it was a very awkward time indeed. Giovanni was probably feeding Mewtwo Calcium tablets orally and it was a very uncomfortable time. Or even eating things like berries, it was probably a very weird feeling having to put all those organs to work for the first time. It probably has difficulty sleeping too because its power is so overwhelming.
Mewtwo dreads the fact that it is not a complete copy, as it's mortal body limits it. In the canon of Mewtwo Strikes Back especially, if we apply this, Mewtwo is probably very annoyed that it must rely on Giovanni to keep it fed and rested.
Idk. Much to think about.
