Quick Answers:
1) The different parts of the electromagnetic spectrum are differentiated by changes in wavelength and frequency.
2) The blue end of the visible spectrum has a shorter wavelength and a higher frequency than the red part of the visible spectrum.
3) radio, microwave, infrared, visible, UV, X-ray, gamma
4) Frequency and wavelength are inversely proportional. This means that if the wavelength increases the frequency decreases and vice versa.