Did you know that the atoms that make you are completely replaced every ~7 years?
I know that's one of those many inaccurate factoids that most people assume are true because they've heard it many times, like the old "we use 10 percent of our brains" myth. In fact, different body tissues are replaced at different rates. Some cells, like blood and skin and stomach lining, are constantly being shed and replaced, while others, like heart and brain cells, and of course stem cells, stay with us throughout our lives. Every woman is born with her ovaries containing thousands of egg cells, only a few hundred of which will go through ovulation before she dies, so those cells and their constituent atoms are with her throughout her entire life. The atoms within cells can be replaced at varying rates, but many of those replacement atoms will be recycled from elsewhere within our own bodies. Studies of people born before and after atomic testing
increased the amount of carbon-14 in the atmosphere have shown that in the former category, most of the DNA in their neurons had carbon isotope ratios consistent with the atmosphere before nuclear testing, proving that most of their neurons were formed in childhood. That proves their neuronal DNA molecules were still made of the same atoms they'd been made of decades before.
As long as you keep making assumptions without having read the book, you'll just embarrass yourself further.
As I've already stated repeatedly, yes, "Data 2.0" has most of the "charateristics" (or at least the memories) of the original, but the crucial point is that he also has new characteristics that the original didn't have. Those memories are being run by different, more advanced software and firmware modeled on Noonien Soong's own brain architecture, so I expect he's going to turn out to have an amalgam of Data's and Soong's personalities -- as I said, like a Trill joining. This isn't about the philosophical niceties of identity -- it's about the fact that, from a strictly story-based viewpoint, this is not a return to the status quo ante, because there are real and meaningful differences in who Data is now, whether or not you believe he has continuity with the original.