Buttstock hole is for bolt disassembly
No- the 7x57 was developed separately, in 1892 by Paul Mauser. The 8mm Mauser (actually the 7.92 Mauser, but every calls it the 8mm) was developed by a government board.
Numerous commercial and custom makers have made 8mm Mauser rifles in the last 100 years
50-160 USD or so
What about it?
No
The 8mm Mauser is a good black bear round. American 8mm is kind of underpowered but with handloading or European ammo its in the same class as 30-06..
Yes....
10000.00
$450
"No, 7.92 is German military caliber for WW 2 and earlier Mauser rifles." Actually, 7.92x57 is the same thing as the 8MM Mauser, if that's what the person was asking.
100-1000 and up depending on specifics
7.92x57mm, better known as 8mm Mauser. Same caliber as the German military's Mausers.