Yes technically but i would go for other upgrades first such as a prometheus barrel or a new cylinder/cylinder head and piston as a good air seal and a consistent fps will give you better range and accuracy then pure fps mine shoots 410 w .25s with stock spring and those mods and i can hit a person at 75-100 yards easily an i still have a great ROF
No
No company makes a spring action galil airsoft gun currently.
go for the m14, unless its cheap looking.
No, it is a cheap spring gun and could not be used in an airsoft match
A spring gun? It depends on how fast you can cock the gun. There is not a fastest gun.
yes
Never buy spring guns
No. even though some spring guns have great range, co2 allows you to fire more then once before reloading.
You can't without some experience in metalwork.
take apart the whole gun
yes
Not AFAIK