Can .380 Auto ammo be fired in a .38 revolver?
No. Don’t do it.
.380
Which Beretta 84 in .380 (84, 84F, 84FS, 84BB) is best for concealed carry?
Any 13-round Model 84 in good shape will carry fine. The later 84F and 84FS (Cheetah) are the easiest to live with: they have a frame-mounted safety-decocker, and parts are easier to find.