How can a three-phase four-wire socket be divided

It's easy to distinguish that a power socket with four jacks is three-phase and four-wire; The top electrode is the grounding electrode, and the other three are the A-phase, B-phase and C-phase power supplies.

a socket with two jacks is a single-phase power socket;

there are two kinds of sockets with three jacks: one is a single-phase power socket with grounding electrode, and the other is a three-phase socket without grounding electrode.