Case length, case capacity, bullet diameter
Yes
380 - 357 = 23
It is: 380 minus 357 = 23
You can only use .380 ACP ammo in a .380 pistol. Period.
No.
No.
A double action pistol that chambers a .380 ACP round. AKA 9mm Kurz
No. 38 = .357 projectiles; 380 = .355 projectiles from a shorter case
Small pistol small pistol primer
The most common .38 is the .38 Special, a rimmed revolver cartridge that is actually .357 inches in diameter. The most common .380 is the .380 ACP. That is a rimless automatic pistol cartridge. It is shorter and slightly fatter than the .38 Special. They are intended for two entirely different firearms, and do not interchange.
357 sig is a cartridge that is a relatively high speed handgun round. It is not a pistol itself, many, many pistols are chambered for this cartiridge.
mike