The problem with detailed is unless someone can do a better job then google it is rather hard for me to give a detailed overview. While not having 2.0 up yet, the
jp alice wiki does contain a list of what 1.6 did.
But generally speaking the major changes from 2.0 are changes to the XP system so you dont go back to level 1 after the first H and a swath of new quests and around 9 new characters + enemies, then the accompaning CG. Maybe in a year or two we will have a translation patch.