Hygiene works because bacteria are flushed out, not because water kills them (ok, antibacterial soap may kill some bacteria, but not much).
Everyone has loads of bacteria all over them, the vast majority of which are completely benign. AIUI, there's a little ecology there, with all of them competing to survive.
So if you kill them all by sterilizing your whole surface, you create an opportunity for the bad bacteria to gain the initiative and take over the ecosystem when the benign stuff can't fight back as well. The end result, then, could be that where you'd had just a few of the bad guys, you're now covered with them.
no.
That's why sterilization uses steam and / or boiling.
But people gave me a lot of crap about using cold water anyway. So part of my process, just to be safe, was to ensure the clean dishes dried very well, next to a window, in the sunlight.
The only stuff that warm water doesn't work well for are as far as I know dairy products and egg-white, because they solidify when warmed up.
Also, there is not much point in thinking you're killing bacteria and then using a dirty dishrag to dry off the dishes :)
Bacteria are pretty hardy, some of them even survive at temperatures above 300 degrees celsius, but you're not likely to run in to them in the home (unless you live in a sulphuric hot spring).
edit: I hope that's 90 degrees Fahrenheit you are referring to.