Of course not!
Not sure what you mean...I believe Afghanistan and Iraq currently require machine guns...as well as Georgia...
Yes
Battles, like any other.
Probably about the same as any other country's machine guns in any wars they've won. We weren't the first to have them - by the time we employed them, our enemies did, as well.
Yes, but not any more than any other gun.
Cost.
Machine Guns, like any other gun (with the possible exception of an air soft gun) could seriously harm, and even kill you if at point blank range. Any gun could kill you, so, yes. a machine gun is powerful.
Well there is assault rifles but not any sub machine guns that I know of.
Pretty much any nation which ever had a military since the 20th Century.
because we have machine guns and tanks and naphalm
They are still made, and are made like any other firearm- by machining metal parts.
There are several different types of machine guns, in several different calibers. You haven't stated any specific type or even class of machine gun which you had in mind.