you could measure. most Skateboarding wheels are between 50mm to 58mm although other skateboards, such as longboards, have bigger wheels that are shaped differently.
it may say it in small writting near the bearing at the middle of the wheel
it might depend on the size of the skateboard but mine are 2 inches exactly
yes you can
50 to 52 mm
A skateboard has 4 wheels.
It is a bad idea to ripstick and skateboard wheels are very different but i don't know if it would work but it probably wouldn't.
no
Wheels dont make a skateboard easier to turn on the skateboard trucks do that.
no
Bones wheels
yes the sizes of skateboard wheels range from 40-70 mm
It is pretty much a wheely on a skateboard but with 2 wheels.