OS without IPv6 support won't translate it to the IPv4 address and connection won't be established? I just guesting....

Depends on the Operating System. Some OS's understand that ::ffff::/96 (ipv4 mapped) is actually an IPv4 address and will initiate an IPv4 connection to the remote host, even though the local application will think it is IPv6, this is almost similar to using ::a.b.c.d/96 (ipv4 compat), but that was deprecated by RFC4291. It thus might work, but in most cases won't as OS's don't support this. But it makes a lot of things really confusing thus please avoid using it and use native IPv6 addresses. (I state native there as using 6to4 addresses or Teredo is also not the most stable address type to put in for instance DNS) See also: Wikipedia: IPv4 Mapped Address Wikipedia: IPv4 Compatible Address