Answer to Question 1
Type M are metallic in appearance, probably fragments of the metal rich core of a broken up parent body. Type S are reddish in color with stony composition, typical of mantle material. Type C are very dark with carbon rich crusts that were never very heated.
Answer to Question 2
Mars will retrograde on the inner portion of its epicycle, when it is closest to us and its motion on the epicycle is more obvious than its motion along its deferent.