For historical reasons, there are a number of IP addresses (some standard and some not) which are used to indicate that an IP packet is an IP broadcast. A router
In the second bullet, the router obviously cannot recognize addresses of the form { <Network-prefix>, 0 } if the router has no interface to that network prefix. In that case, the rules of the second bullet do not apply because, from the point of view of the router, the packet is not an IP broadcast packet.