Can a stored pressure water extinguisher be used to extinguishing all types of Class B fires.?

Certainly not ! Class B fires include petrol/oil fires as well as grease (chip pan) fires. Using a water extinguisher will not extinguish these types of fires because - since the flammable substance will float on water - it simply heats the applied water, turning it to steam - resulting in an explosive 'cloud' of burning vapour.