Explanation:

Reference:
https://docs.microsoft.com/en-us/azure/virtual-network/ipv6-overview
https://docs.microsoft.com/en-us/azure/virtual-network/ipv6-add-to-existing-vnet-powershell
1) Correct: /64
Explanation: The subnets for IPv6 must be exactly /64 in size. This ensures future compatibility should you decide to enable routing of the subnet to an on-premises network since some routers can only accept /64 IPv6 routes.
Source: https://docs.microsoft.com/en-us/azure/virtual-network/ip-services/ipv6-overview
2) Correct: Public IPv6 Address
Explanation: Add IPv6 configuration to NIC. "Configure all of the VM NICs with an IPv6 address using Add-AzNetworkInterfaceIpConfig" Source: https://docs.microsoft.com/en-us/azure/load-balancer/ipv6-add-to-existing-vnet-powershell