please state the make and model. It will make it easier to answer your question.
Use C02 to propell the pellet
It all depends on the model.
100 USD
CO2 pellet guns work by using CO2 for rapid fire, with CO2 the gun does not need to be pumped or recorked after every fire. You can also find spring loaded pellet guns.
They are about the same, depending on the pistol. C02 has a tendency to be a little louder on certain pistols but not much difference.
Pellet guns are more powerful. They are stronger because they use a CO2 Gas, whil BB guns are spring-powered.
Contact the maker for a replacement manual
Follow instructions provide with the item. If you don't have them, contact the maker.
The Crosman 120 is a rifle not a gun. It is a break barrel. Cock the barrel all the way down and load a pellet into the rear of the barrel. Pull the barrel back up and it' is ready to fire.
The Crosman model 150 was made between 1954-1967. It is a .22 cal pellet pistol.
If you mean the standard 12 gram CO2 cartridges, they are not reusable.
CO2 powered weapons are usually fitted with a removable cartridge - which is stored in the handle of the gun.