Futurology

The motor cortex is located in about the same spot in everyone, to my knowledge - I don't know of any reported exceptions. The pre-central gyrus. Within, motor neurons are organized in specific regions that control specific body parts. Again, I don't know of any reported exceptions - my understanding is everyone's motor cortex has the same organization. It's known as the cortical homunculus. https://en.wikipedia.org/wiki/Cortical_homunculus#Motor_homunculus%3Fwprov=sfla1

So by reading output from a small group of neurons, yes, you could control a prosthetic limb. It's been done a few times, actually! But, you typically need more precision than comes from an EEG electrode, so all the examples I can think of are using invasive electrodes.

In fact, the sensory system of the brain has a very similar organization - along the postcentral gyrus, and the same stereotyped organization within. If you could stimulate the correct region of the sensory cortex, you could create a prosthetic that allows you to feel.

There are some more technical limitations though - there's different types of sensation (e.g., pain, temperature, proprioception (position in space), texture, etc.) that are controlled by different receptors in skin and have different wires connecting to the brain. You'd have to be very careful about what you stimulate. And, any implant that delivers electricity to the brain, with our current technology, has a limited lifespan due to the brain's immune system rejecting the implant (this is the aspect I studied).