"33.  [Ans.] We cannot fully understand..."
BC gets as far as can be gotten in the format, through reason and revelation.  It's not meant to be an intellectual exercise beyond learning the basics or improving memory.  It does what it is intended to do - offer a summary to children.  Adults learning the basics for the first time might go to something deeper like the Catechism of St. Thomas Aquinas, the Catechism of Trent, the Catechism of the Catholic Church, or to some of the key documents themselves (conciliar extracts, encyclicals, etc.).  That said, some adults would still benefit from the clarity of BC.