The speed of light is the speed all waves travel ?
No, only the speed of all electromagnetic waves.
It's different for ocean waves, rope waves, sound waves,
guitar-string waves, slinky waves, etc.
The speed of light is the speed electromagnetic waves travel ?
Yes. Light is one of the electromagnetic waves.
The speed of light is 3.0 x 108 m/s in space ?
Yes. That's a good approximation, and a nice easy number
to remember.
It's only about 0.07% faster than the real number: 2.99792458 x 10⁸ m/s .
The speed of light is the same in all matter ?
No. It's different in every substance, and the speed in any
substance is less than the speed in space (vacuum).
The speed of higher frequency light slows down
more than lower frequency light in matter ?
Yes, slightly. That's why the colors spread out on the way
through a prism to make a spectrum, or on the way through
raindrops to make a rainbow.