1) Any gov, state or local legislation takes precedence over any bylaws and if the bylaws conflict with any law the bylaw looses.
2) Generally Structural repairs are the responsibility of the Strata unless a bylaw has been duly passed transferring that responsibility to the lot. Cosmetic repairs are the responsibility of whoever is responsible for the item (common property or lot property).
3) yes responsibility for common property can be transferred to lot owner (and subsequent owners) by a special bylaw being passed and registered with the state gov.
Structural items (especially in a unit situation) should not be transferred to lot owners and in your situation I would say the original balcony balustrades are still OC responsibility but the additions belong to the lot owners and the only thing the OC are obliged to do are remove them if considered unsafe as they are unapproved additions.