A very interesting question.
1) Only one rank fires in a wood so do they get 1, 2 or 3 dice? I.e. if it is only one rank MUST it be the first rank?
Page 139 - Troops inside can only shoot in 1 rank. Page 88 - Terrain that only allows shooting in 1 rank prevents all shooting and support shooting from a 2nd or 3rd rank. I therefore believe that you only shoot with the 1 front rank base in this example. The 2nd rank bow normally shoot from the front rank position but this is specifically prohibited in this scenario.
2) They want to charge the medieval cavalry do they have to test to charge as they have bows in the front rank?
This one is more clear cut. Page 64 - Non-shock medium foot whose front rank has bow etc must pass a CMT to charge or intercept...So yes, I believe a CMT is required since you have MF bow in the front rank.