One thing you come to appreciate through the study of history is that people weren't stupid. Just because they don't have iPads and blogs doesn't mean they were less capable, as individuals or as a group. If you compare the current state of elected officials today to 200 years ago, you'd come to appreciate it too.
An interesting thought experiment is to assume a group of engineers, with perfect understanding of our modern technologies and how to make them travel back in time to the stone age. How long would it take for them to arrive back at our current technology knowing what the critical path to do so would be?
The single-person question is an interesting one. My instinct is to say: "let's try it". Of course I begin by performing a mental simulation. And it then occurs to me that this might be expensive, time-consuming, very, very difficult (especially obtaining materials!) but most of all dangerous. I suddenly wonder how many people have been maimed or killed developing modern (manufacturing, especially) techniques. Even if it's possible for one person to do; what are the odds of survival?
Ok let's make intermediate challenges, maybe not current tech, just enough to survive comfortably. Function of some context (different paths whether you start in Africa or Russia because of material, climate and such)
- math/physics knowledge to assemble tools
- having regular heat sources
- building a small shelter
- regular nutrient sources
then there's room for
- increasingly precise and versatile tools
- finding ways to generate and store electricity (wind, water)
- light
- optics
- radiowaves/communication
