Question 1: "display a snippet?" Not without using an entirely different approach. MD5 is useful ONLY to compare the totality of the files; not of segments. If you really want to know what the differences are, use a tool built for that purpose, or write your own tool using line-by-line comparison (yes, you could do it para by para or use some other unit, but the concept is simple enough line-by-line.).

Question 2: MD6? Why? What-on-earth-good would that do?