Got some questions about a pIII

Here are a few Q's:
I got a 866 pIII and a MSI 815e Pro (MS-6337)

1) Which is the best operating temp.

2) How high can the voltage go before it becomes harmfull.


And I might have more just gotta think about it.

Intels specs for the coppermine state that 2.1volts is the maximum.