The human brain is designed to live inside an innervated body. It receives constant updates on how the body is doing, and unconscious processes, some of them chemical, control every aspect of our internal life, from homeostasis, to the perception of time, to breathing, mood and muscle tone. Upset one part of that balance and the brain goes into blind panic. Although the brain also has electrical activity, it is not just a sophisticated computer program running on a general purpose computer. For one thing, the hardware is unique in every individual! Secondly, what makes you you? And what is consciousness? We have no idea. Perhaps it is not possible to reconstruct the real you, rather than an emulation of you, without copying the exact quantum states of the atoms in your body. But this may require complete destruction of the old you and construction of an identical quantum copy elsewhere (teleportation), which is hardly an electronic download of "data" into a computer. You might be able to extract your memories and store them in a Von Neumann architecture, but the rest is a pipe dream.
A computer with input and output, yes. Some representation of relevant neurotransmitters and sensory inputs and such seems necessary. Think whole brain emulation, rather than extracting the "mind information" while ignoring all the physical information.
And if I make 100 copies of this computer program and run them on 100 different computers, which one will I be aware is me? Or will I just be aware of being 100 different beings at once? I think it should be obvious that a simulation of reality is not the same thing as reality itself. For one thing, perhaps we need to know a lot more about how the universe works at the quantum level to even emulate reality faithfully.
They are all you, until they start reacting differently to their different inputs and anything stochastic within their simulation, and at which point they stop being "the same" you is basically up to you. The difference between them after a minute or two would probably be nothing compared to the difference between you and you a year ago; if you call the latter "you", the former should probably count too. You wouldn't be aware of being 100 beings, but 100 yous would be aware of existing.
Calculating down to the quantum level is hopefully not necessary (that seems impossible to get efficiently out of any computing substrate physics will let us have). The few people suggesting that physics at that scale impacts consciousness aren't taken very seriously by neuroscientists in general.
Might not do. There have been experiments with people with mental issues or just general experiments abusing or cutting nerve endings in different ways and a lot of the more radical ones (like this would be, at least for the first 1000s of subjects) end up in insanity. And you would rather be dead I think.
