From the North side, locate a vertical crack that starts 20' off the ground. This is the "Backside (North Face), 5.9". Instead of following the nice crack to the summit, delicately hand traverse up and right for 50' or so along various types of holds (some greasy, some bomber edges, some questionable edges, some cool, upside down huecos) to the rappel ledge, then up the easy 5.2 route to the summit.
The crux of this route will be just getting to it! I soloed the North Nostril and didn't feel like descending that route, so instead I just followed this natural ramp / hand traverse down. Eventually, I had to stem out to the very top of a medium-sized pine tree while using sketchy flakes on the rock to get back to the ground.
Can't say I recommend it, but it is probably a safer downclimb than the North Nostril.
This route is waaay out there. The best approach is probably to hike to Sentinel Pass, then head straight up on the North side of the 4th Flatiron, Green Mtn. Pinnacle, and Challenger. Once above Challenger, head left over the ridge and you'll run smack into it.
No idea. Maybe a few nuts and a medium/small cam for the bottom of the 5.9 crack, but mostly you'll just have to pucker up and send.