The SKU can be either basic or standard. The main difference is that standard is closed to inbound traffic by default (inbound traffic must be whitelisted in NSG), and standard is zone redundant. Another difference is that a standard SKU public IP address has a static assignment and a basic SKU can be either static or dynamic.
You can choose either the IPv4 or IPv6 version of an IP, but choosing IPv6 will limit you to a dynamic assignment.
The DNS name label is optional, and it can be used to resolve the endpoint in case a dynamic assignment is selected. Otherwise, there is no point in creating a DNS label, as an IP address can always be used to resolve the endpoint in case a static assignment is selected.