Final answer:
IPv6 unicast addresses are used for one-to-one communication to identify a single network interface. Not all IPv6 addresses start with "2001", as that prefix is specifically for Global Unicast Addresses. Also, unicast addresses are not assigned to multiple devices simultaneously and can be assigned dynamically in various ways.
Step-by-step explanation:
The characteristics of IPv6 unicast addressing described by the question can be understood by looking at the nature of unicast addressing. IPv6 unicast addresses are used to identify a single interface in a network (Statement B). Unlike broadcast communication, which is not supported in IPv6, unicast addresses are designed for one-to-one communication, hence there is no concept of one-to-all as in broadcasting (thus disproving Statement D). Additionally, while IPv6 addresses may start with various prefixes, not all IPv6 unicast addresses begin with the prefix "2001"; the "2001" prefix is specifically for Global Unicast Addresses (GUAs), and thus Statement A is incorrect. Moreover, unicast addresses are not meant to be assigned to multiple devices simultaneously; each unicast address is intended for a unique interface (disproving Statement C). Dynamic assignment of IPv6 unicast addresses can occur, but it is not exclusively done by network routers. There are other ways in which IPv6 addresses can be assigned, such as Static configuration, Stateless Address Autoconfiguration (SLAAC), and DHCPv6 (making Statement E too narrow a description).