1) the robes of shaolin monks are based on the rules for monastic wear set up by the buddha. usually they were made with cast-away cloth, or sometimes from a corpse. nowadays monastics dont need to do that and it would be rather strange, honestly. rather the laity often supply monastics with new sets of robes. the colors are usually autumn colors such as orange, red, yellow, and brown. the color represents the turning of the leaves in autumn just before they fell. which is a symbol of detachment or renunciation. nowadays though, especially in shaolin you'll see all types of robes with fancy material and color. this is a modern thing. some robes are even made with only one sleeve. originally, in india when a pupil would be in the presence of a master they would remove their sleeve to uncover their right shoulder which was a sign of respect. most buddhist sutras start with someone approaching the buddha, removing their sleeve to uncover their right shoulder, kneeling on one knee and joining their palms- which was the formal way to make requests or ask questions to the buddha.
2) most styles of china are based on aspects from shaolin or even have history there. but most were not actually practiced or taught at the temple but developed elsewhere, sometimes based off of shaolin arts. such as "bak siu lam" in cantonese which means northern shaolin. this style was created in the south, hence the cantonese title. but was based on what the creator had learned from the temple in the north, hence the honorary title of northern shaolin. however, there is no real evidence of it having been practiced or taught in the temple, though it is certainly related. similar events are the case for styles such as wingchun and hungga. styles such as baguazhang are daoist, having nothing to do with shaolin buddhist arts. the first style created in shaolin was rouquan which was an internal style much older than taijiquan. but later, an ex-general from henan, chen wangting created the first taijiquan style named after his family, chen style, from chen village (chenjiagou) in henan province. since it was very near shaolin at one time they had a crossing and shaolin has adopted chen style taijiquan, which is similar to many other styles in history. but at shaolin the taijiquan practiced there is following the chan philosophy, so it is known as chan style rather than chen. it is slightly different yet obviously from chen style taijiquan which was created and developed outside of shaolin in a non-buddhist foundation.
3) i'm not sure of any graduation or mastery. but it is very common for masters to send their disciples to travel to other temples to learn more about buddhism. even today. one of my masters has been ordained and lived in three different temples in henan and is currently outside of henan following his masters wish for him to travel more to learn about buddhism. there is no requirement for them to be sent or allowed to go. they just follow their master. yet in some temples it is common for a test to be passed in order for the monastics to open another temple or center elsewhere, for obvious reasons. but for travel and learning, there is no requirement.
4) again, not sure about any specific "graduation". but each person is different and so each person is taught differently and naturally they will progress differently as well. so time for anything is always relative. imagine a requirement of only three years but you have a slow learner. would three years be enough to pass him although he has not grasped the teachings?
hope this helps!