The explanation for why Ashley's entire personality in the Ashley Too dolls isn't just a Hand Wave, as any real-life neuroscientist probably knows, separating a chunk of the brain and activating it wouldn't work, due to the neurons being connected to other surrounding ones. However, as shown in real life coma patients, as long as the neurons are still there, single chunks of the brain can work by themselves.
Moreover, although they don't use the word, the internal logic of how the Ashley Toos work was already established by the "cookies" that first showed up in "White Christmas".
Related to the above. While the Ashley Toos are clearly based on cookies, as they are perfect copies of somebody's mind and can be installed into inanimate objects (as seen on earlier episodes), their functionality doesn't appear to be based on torturing and basically conditioning them into servitude, as it was on such episodes, but is based on a mere limiter that selects specific parts of the cookie's brain to interact with. Sounds like some sort of Retcon or Plot Hole, until you remember that, unlike the cookie device or the teddy bear, the Ashley Too actually is supposed to respond with a degree of awareness and autonomy, and interact in a cheerful way, not like a suffering slave.
Also, even in-universe, the treatment of cookies is reviled and considered inhuman and this method actually SPARES the copied consciousness any existential angst and the need for prolonged conditioning, to the point that they are barely in any pain and suffer no lasting repercussions. Indeed, when Ashley's full personality is unlocked, while she seems somewhat aware and smothered by the limiter, she is very much her own normal self and shows no signs of any torture or conditioning. Even more so, unlike the severely limited cookie device or teddy bear, the Ashley Toos are fully autonomous, speech-capable robots with cybernetic limbs, which provide the cookie full agency.
Why does the Ashley Too not seem to know any vintage bands when talking to Jack, when the real Ashley would no doubt know exactly who Jack was talking about? Would you advertise or bring attention to any competing brands when your product is designed to get young girls to buy more of your merchandise?
Most likely it's the limiter denying any access to knowledge about other artists. Plus, whoever made the Ashley Toos probably didn't want them singing copyrighted music (or any music not owned by Ashley's label).
Why would Aunt Catherine hire someone so incompetent as Bear as a bodyguard and produce products like Ashley Too that turn out to be easily hacked? Cost-cutting. Catherine wants to maximize profits wherever she can. A true professional bodyguard wouldn't go along with committing crimes like false-imprisonment and murder, but someone more along the line of a bouncer type with little or no training would. Her accomplices have the same attitude: they're greedy and short-sighted, which ultimately proves to be their downfall.
In fact, related to above, Ashley's rescue and Aunt Catherine's exposure boils down to mostly dumb luck, a single Ashley Too being spared from a product recall, and the compassion of two young women who just happen to be in the right place and the right time to help.
Ashley Too isn't upset about being in a robot body after her limiter is removed because it's the first time that she's in total control of herself, mind and all. Her Aunt's control over Ashley Ortiz extended to how she dressed, appeared, and acted, including what to eat and how often to exercise. So, being in a body that she has total control over and being able to use her entire mind again would be a welcome relief after years of abusive control.
Even if Rachel's doll wasn't woken up, it was only a matter of time before someone else—a security researcher or a budding computer hacker—did exactly what Jack did. Which means that sooner or later, Catherine's criminal scheme would've been exposed. Again, it was just dumb luck that Jack and Rachel were the first ones to do it.
This could even have been inspired by what happened with Teen Talk Barbie in real life, including a protest group organizing several hundred of the dolls to have their voice chips switched with those of talking G.I. Joe figures. If the technology back then had been sophisticated enough to be hacked, someone would have done that too.
If you pay attention to the lyrics to "I'm On A Roll", they actually make little sense - the verses sound like a love song while the chorus is about optimism and setting goals, with no common thread between the two ideas. This lends itself to the idea that "Head Like A Hole" is the original version in universe too - Ashley probably submitted that set of lyrics to Catherine at some point, and Catherine went about censoring them, focusing more on making the content appropriate for a tween audience than having the end result actually be coherent.
Rachel's Ashley Too doll could not have been the only one that escaped the product recall. At the very least, the things would certainly be collectors' items. Given how easy it was for two teenagers—who didn't know how to use the software—to remove the limiter, it's possible that other Ashley Too dolls are out there in God knows whose hands.
Rachel and Jack feel a bit betrayed that Ashley Too lied to them about gathering evidence against Catherine, when she only wanted them to drive them to her house to pull original Ashley off life-support. But Ashley Too's memories were outdated; the dolls were created before Catherine revealed that she found Ashley's journal and laptop, and she most likely destroyed them after she put Ashley into her coma. If Ashley Too hadn't lied or tried to pull her original body off life-support, Catherine would have killed her and gotten away with everything.