Almost.
I've seen a horribly cheap toy skateboard once that didn't have bearings, only a plastic center to the wheel.
But apart from that, any time you buy a complete skateboard it'll come with bearings.
No. Skateboards and inline skates all have cartridge bearings, while a lot of bikes have cup & cone bearings. For those bikes that do have cartridge bearings, their axles are thicker than skateboards/skates.
Not if you are buying the trucks separately.
for price, yes*. for durability, no*. speed depends on what bearings you have *not by much
They go in the wheels to hold them on the trucks and let them spin.
Rodney Mullen uses Speed Demons bearings on his skateboards. These bearings are typically described by riders as smooth and quiet.
the parts... deck trucks wheels bolts bearings and griptape
go 2 local skateshop get their deck and very good trucks and bearings independent trucks, lucky bearings and spitfire wheels
Pretty much. Most skateboards, quads, inlines and scooters use the same industry standard "608" sized bearings.
No, skateboards came before BMXes.
INA Bearings make a wide range of ball bearings and their inserts. These are used in a wide range of products, though they are best known for their use in skateboards.
Trees
because the wood is bad quality and won't last long and the trucks and bearings are useless.