That last one is the handheld "Villar Perosa" double submachine gun, made up from two inverted Beretta 38A submachine guns, a Bren LMG front grip, and a trigger group from an MG42 machine gun.
The bottom pic in your first set is a real Villar Perosa that was mounted on a motorcycle, it was in caliber 9mm Glisenti and they had a real bipod.
The top pic in the first set is a Villar Perosa Mod. 1915, designed for use in aeroplanes as a flexible observer's gun.