Diffrection: Single Slit to Many Slits

This is intended to be a very quick overview of single slit diffraction:

And a diffraction gratings.

Question 1: Similar to double slit interference, single slit diffraction patterns are the result of path length differences. Explain how it is possible to generate an interference pattern with just one slit.

Question 2: Diffraction gratings are most useful to separate light in to peaks of different colours. Explain why a peak light intensity for blue light ends up in a different position than a peak light intensity for red light.

I am expecting something very brief. ( A short paragraph for each explaining each concept from the perspective of wavelength and path length difference).