Is it possible for someone to send an IP broadcast packet over all internet? I know that routers do not allow that, but is there any other way?
(IP=255.255.255.255) are not forwarded by routers. Devices that do are called bridges or switches, not routers.
(IP=192.0.2.255/24) could be forwarded to a specific network, if the router was specifically configured to do so. But routers on the Internet are never configured that way.