Whats the most challenging and scenic gravel bikepacking route that can be completed in under 3 days, with minimal road riding and maximum elevation gain, and which routes offer the best balance of technical difficulty, scenic beauty, and logistical support, such as bike shops, food, and accommodations, for riders who want to push themselves to the limit, and are there any routes that offer a true wilderness experience with no cell phone signal and limited access to amenities, and how do riders prepare for and navigate these types of routes, and what are the most common mistakes to avoid when tackling these types of routes, and are there any routes that offer a unique cultural or historical experience, such as riding through ghost towns or following historic trails, and how do riders balance the need for solitude and self-reliance with the need for safety and support on these types of routes.