That is enough questions to fill a book.
The original, basic, and standard Mauser caliber was 7.62.
The 9x25 Export is said to have gone mostly to South America.
The 9mm P "Red Nine" was made as a substitute standard WW I German military pistol. There were also 7.62s in use, which is why the 9mm grip was marked to keep ammo requirements clear.
The detachable magazine came in with the 1932 Schnellfeuer Model 712 full auto in 7.62 only. There is such a thing as a Model 711 detachable magazine semiauto, but even the Blue Book says most that you will see are fakes, Schnells with the selector cuts welded up (and still illegal.)
There are Spanish copies and Chinese copies of most any combination of features you can imagine.
Then when the Communist Chinese unloaded their surplus guns on the American market, there got to be even more versions. Fed Ord bought up their Schnells, scrapped the full auto frames and made new semiauto frames to sell a fake 711 detachable magazine broom. I think some of those were rebored or rebarrelled to 9mm; so you can have a 9mm 20 shot if you can find one of them. Just don't pay an Oberndorf price.
CAUTION: A friend of mine had his shot-out Chinese Bolo rebored to 9mm. The barrel looks ok, but they did nothing to the magazine (One of those shops that don't want you to send in the lower, probably don't even have a FFL to work on a whole gun.) and feeding with the shorter round is not reliable. So think twice about altering a 7.62 for cheaper ammo.
They made up a number of other repros and imitation repros. That is, guns that look like they are repros of something that might have been made by Mauser, but probably never were.