what's IPv6 analogue for IPv4 `arp -an` and "arp who-has"?

ip -6 neigh show 

Above command is to check arp table for ipv6

Neighbor Discovery Protocol (NDP) is the IPv6 equivalent of the Address Resolution Protocol (ARP), and on the Unix flavors I'm most familiar with (mostly BSDs) the ndp(8) command is the IPv6 equivalent of the arp(8) command.

The command-line options for ndp are often the same as for arp, so ndp -an does exactly what you'd expect.