This scenario describes the classic router-on-a-stick inter-VLAN routing design. A single physical interface on R1 connects to switch S1, and multiple sub-interfaces are created on that physical interface to serve as gateways for multiple VLANs. Therefore, if R1 provides Layer 3 gateway functions for VLAN 2 and VLAN 3, sub-interfaces such as GE0/0/1.2 and GE0/0/1.3 must be configured, so option A is correct.
Because PC2 and PC3 are connected to switch S1, S1 learns their source MAC addresses dynamically and stores them in its MAC address table, making option B correct. R1 receives tagged frames from different VLANs on the trunk link and, through its sub-interfaces, can identify and terminate frames for VLAN 2 and VLAN 3, so option C is also correct.

The address 224.0.0.1/24 cannot be configured as a normal host IP address by default because it belongs to the Class D multicast address range. IPv4 multicast addresses range from 224.0.0.0 to 239.255.255.255 and are reserved for multicast group communication rather than assignment to host interfaces as ordinary unicast addresses. Therefore, option D is correct.