Impressive numbers. Let's hope it's a big improvement, the 5800x3d is still a monster for gaming. If they don't take a solid lead it's not going to look so good for AM5 vs Intel's latest.
They won't do that. Because of the way the arch is designed it boosts to thermal limits, not clock limits. The cooler the chip runs the faster it runs. IE, IDR exactly what the thermal limit is (90?) but it will boost until it gets to that temp regardless of cooling solution. As such if you lower the temps it will boost even higher. Something they clearly don't want to happen (mostly because the chip is probably running at the safe limit as it is).
Obviously if you mod your way around it you lose any warranty, so at that point it isn't their problem any way.
These X3D chips are fragile. Such is the way when you put stuff on top of other stuff. As to how they will bode long term? remains to be seen. Kinda like how a lot of the HBM cards are dying now.