No, the 9mm won't feed. But you can feed .380 in a 9mm. Bad idea. Always double check your ammo and weapon. And don't assume your wife grabbed the correct box out of the truck.
I have a 380 Llama - Looks like a scaled down .45 and was the RAF pilots sidearm in WWII. Friend of mine has a 9mm Luger.
NO - the 9mm will not fit in the 380's clip - the cartridge of the 9mm is considerably longer - I believe the diameter is identical however.
No. Semi-auto, rimless cartridges depend on having the case mouth (where the bullet is crimped into the brass) settle on a rim at the end of the firing chamber. This places the case head (where the primer is placed) in exactly the correct spacing for the firing pin to strike. A .380 ACP (9mm kurz) will slide down into the chamber and stop at the rim. The firing pin can't possible reach the primer. The 9mm, if placed in a .380 ACP chamber will protrude a great distance. The slide will not close and (hopefully) a safety mechanism will block the hammer from striking the firing pin.
This same technique of setting the headspace using the case mouth is also employed in the .45 ACP.
You should never put any ammo into a firearm unless is is specifically designed to handle that ammo. It is dangerous to do so. At the minimum, you may be disappointed when it doesn't fire. The worst case is obvious.
Bullet weights for the .380 ACP range from 85 gr to 110 gr. The .380 ACP uses a .354 caliber bullet. Same as the 9mm. The .38SPL uses a .357 caliber bullet in weight ranges from 125 gr to 180 gr.
No, a .380 is a 9mm short, 9mm Luger ammunition is too long to fit in the chamber. You can fire a .380 in a 9mm Luger but it likely won’t cycle reliably after the first shot because the magazine is not designed for the shorter ammunition. Longer 9mm cases will not chamber in a .380 and firing 9mm Luger ammunition in a .380 should not be attempted. 9mm ammunition in general is loaded with heavier bullet, the case holds more powder, and greater pressure is generated when the bullet is fired.