Silencers are just for looks and barrel extension so it can supposedly be more accurate. Dont waste your money on one.
It's not a waste of money for the extra range and precision you'd be getting. Mock silencers are made yes, for looks, but also so that you have a longer outer barrel length, allowing for a longer inner barrel.
stuff
It's unlikely a clone will last you more than a year, most people replace the parts of clones asap, as said before, It's never a good idea to leave a clone stock.
I have very basic knowledge of airsoft guns, and feel free to correct me when wrong professionals.
Gas I think is when a metal cartridge of carbon dioxide is used to make the gun semi-automatic. Semi-automatic means that you do not need to pull anything to make a bullet fire, just pull the trigger.
Spring is non-automatic. You have to either pull something to make the gun fire or for a pump shotgun, push down on the pump.
Automatic gas guns exist, and alot of gas guns work by putting Propane/Green Gas/Other type of gas into the magazine.