Yes 1 per prestige.
You prestige by making it to the last xp level online then when you pass it you restart and after 10th you cant pass the final level
Firstly You Have to Achieve Max Level Which On Mw2 Is 70, After Completing The Remaining Xp On Level 70, Click On Barracks And Press "Enter Prestige".
Yes, everything in the Barracks resets besides your title, emblem, and clan tag. But if it's your first time to prestige, then you get the Challenge category "Prestige." Plus, you get two new...
No you can not. The only way you can complete prestige challenges is by prestiging.