Today I learned that the 3rd (OC3) survival world has block damage by mobs turned to off. This disables many abilities including but not limited to the following:
(1) ANY kind of restone build in which a sheep eats (They wont eat grass changing the block) the grass triggering the redstone..
(2) You cannot breed villagers due to them not harvesting the gardens or picking up carrots/potatoes/beets when dropped