Choose IPv4 or IPv6 and a safe address range, set how many addresses you need, then press Generate and copy the list.
No, and that is deliberate. The generator uses the reserved documentation blocks (192.0.2.0/24, 198.51.100.0/24, 203.0.113.0/24 and 2001:db8::/32) and the private RFC 1918 ranges, so nothing you publish points at somebody's real server.
Use documentation ranges for tutorials, blog posts and screenshots, private ranges when you need addresses that look like a LAN, and IPv6 when you are testing dual-stack code paths.
Yes. Set the count to produce a list of addresses at once, then copy them straight into a fixture file, a test seed or a config sample.