Skydiver jumps from 25,000ft without a parachute, lands in a net

I can only attempt to add some light to question 1.

There are a number of things which contribute to the level of difficulty regarding this stunt.

Obviously the size of the net is important, I haven't watched the video enough to have a guestimate.

When I first heard about it I kind of scoffed at the fact that they exited at 25,000 feet. It really struck me that they did this just to build more hype with big numbers and longer freefall time. The upside is that the jumper has longer to fly into position, but I think that would be off set by the added difficulty of spotting the exit.

The term "spotting" in skydiving means deciding the point where you exit the plane. You have to factor in the various wind directions and speeds in the volume of air you're going to fall through. With GPS much of the "art" of spotting has been replaced by science, but there is still a lot of skill required to spot a 25,000 foot exit for someone who isn't wearing a chute and intends to land in a net.

Beyond the obvious things, the final "flip over onto his back" part is the terrifying bit for me. I'm sure he practiced this in a wind tunnel many many times, but the chances of your fall path changing from directly downwards is very high while turning over. In the video it doesn't even look that graceful (watch some videos of very good jumpers in wind tunnels as a comparison).

The ground rush effect must have been utterly intense. As you get lower and lower the feeling of the Earth rushing up to you is incredible. I've only ever had 1 low opening (at ~1,200 feet, after cutting away my main chute due to a malfunction); I was no where near terminal velocity but damn did the ground rush up at me while I waited for my reserve to open.

All in all, I'm not actually that amazed that it has been done. The physics are well known and everything involved can be easily tested and perfected. That said, I am impressed by the sheer guts of actually doing it.