Different wavelengths are bent at different angles, which is why you always see them in the same order.

Yes, every rainbow looks the same. Rainbows are an illusion caused by the way light bounces around inside spherical drops of water. The angle light is bent as it passes from air to water and back again depends on wavelength.

They are frequencies, it's the same order because red is the lowest frequency and violet is the highest frequency. When light hits water its path is bent based on it's frequency.

This one is kind of hard to explain without pictures... or in a timely manner. Basically when the visible light goes through the medium that splits it into the rainbow it changes angle, and part of what determines how much the angle changes is the wavelength. The reason the order and ratio is the same is because the rainbow is basically the colors ordered from longest to shortest wavelength spead a based on the change in wavelength. For instance, if you pointed a light that contained all wavelengths but yellow at a prism the rainbow would look the same as it would with all colors with a missing band where the yellow would be because the absence of yellow light does not affect the wavelengths of the other colors. That last bit is actually super important in a handful of scientific fields.