How to computer clouds charge me for CPU usage

Attach WinDbg + sos and run !runaway. That will show you which thread is taking the most CPU time. Do a !clrstack on the thread to find out what it is doing.

If you have adequate cooling, then no. In general, your computer should be able to sustain 100% load for long time. (I've run my laptop for days under 100% load for CPUs and GPU and didn't have any problems).

Also, if your computer is relatively new (say less than 5 years old) it will shut down automatically in case it overheats.

My recommendation is to get some sort of hardware monitoring program like HWMonitor for example and run it while running your task. If the temperatures rise to dangerous levels (I can't tell you what is dangerous for you, since you provided almost no information), you'll be able to see and stop the demanding program.

Also the temperatures will rise quickly, so if they aren't dangerous after 20 or so minutes, then they probably won't reach dangerous levels.

Another thing to watch out for are low voltages. HWMonitor will provide voltage readings. They should be within ±5% of stated voltage for positive voltages and within ±10% for negative voltages. If you do overload your PSU, it should also automatically shutdown, but on cheaper units restarts and Bluse Screens of Death are possible too.