Fall apart=come to pieces
Fall back on=turn to sb/sth for help when other plans have failed
Fall behind with = fail to keep up with
Fall for = 1.fail in love with sb 2.be deceived
Fall in =collapse
Fall in with =agree with
Fall into=1.be divided into (categories) 2.begin;enter a state
Fall on=1.attack 2.eat hungrily
Fall out with =quarrel
Fall through =fail to be completed