Per the recommendation of ppl, I'm breaking this question out into separate posts, so here goes:
Is it feasible for me to plot my own route through the Andes, as opposed to keeping to established trails? My thinking on this is that it will be doable as long as I take precautions such as carrying a satellite phone, keeping within a couple days' range of towns when possible, and avoiding river crossings. That said, I'd appreciate the input of somebody more acquainted with this particular mountain range.
To provide some additional background, I will be alone and I intend to travel exclusively by foot. I won't be attempting any climbing. My main concern is about the traversability of the terrain between Lima and Cusco, especially at higher elevations.