Those are all ways of allowing ipv6 to address ipv4, (or tunning ipv6 over ipv4 infrastructure) which is fairly easy to manage (getting the reverse connection s

Those are all ways of allowing ipv6 to address ipv4, (or tunning ipv6 over ipv4 infrastructure) which is fairly easy to manage (getting the reverse connection still involves NAT though). None of them are ways of allowing ipv4 to address ipv6, because that fundamentally doesn't work by the pigeonhole principle.