Well, not necessarily. In bios you usually don't have the option to change cpu shut down temp. You may set the temperature that you will get a warning of but something around 120 degrees is set directly to both motherboard and cpu, which means if one sensor failes, the other one should shut the cpu down to prevent it from burning. In AMD cpus it has been working since Athlon64.
I guess so, at 90-100 it should reduce clock and at 120 shut down. Well, at least that's what I observed with my cpus. (Pentium D 920, C2D e4700), Haven't actually checked it with my 1090t but I guess it's not worth it. Oh, GF8500 actually never shut down, even at 120+.