Usually not. The 9mm Parabellum catridge is longer than the .380, as a result, a 9mm magazine is also bigger, and the magazine will not fit in the .380 magazine well.
Yes, a Glock 19 9mm magazine can be used on a Glock 23 since both firearms are chambered in 9mm.
No
No. It depends on the make and model of your 9mm and what kind of magazine it was designed to take. In the past automatic pistols each had their own magazine and they were very seldom interchangeable. Today there is more interchangeability, but there is as yet no universal magazine that will fit into every 9mm.
The 9mm was standard among NATO (and most militaries who weren't somehow in bed with the Soviet Union), it has lower recoil (which makes it easier to control), a higher magazine capacity, and single actions designs were at a point where they were considered outdated.
no
Depends on which 9mm. In general most are magazine fed semi-automatic guns. Remove the magazine by pressing the magazine release. Press cartridges into the magazine, insert magazine into firearm, draw bolt or slide back, releasing it, and allowing springs to close the action.
The Glock 17 (full-size 9mm) holds 17 rounds in a factory magazine. The Glock 19 (compact 9mm) holds 15 rounds in a factory magazine. The Glock 26 (teeny-tiny 9mm) holds 10 rounds in a factory magazine. The Glock 17L/34 (competition) also holds 17 rounds.
Yes
No
First it is Beretta, second, it is a magazine, not a clip. There are several different 9mm models made by Beretta- it will use the magazine made for that model.
probably not................... The magazines are similar, but the 9mm has a spacer in it on the rear of the magazine to accomodate the shorter 9mm cartridge. New magazines in both calibers are available from Colt on their web site (Coltsmfg.com). Ps: a "clip" is a strip of metal made to hold rounds by their base, (google firearm clip) a magazine is a spring loaded box like receptacle where you put rounds in.