What is the correct process for the TCP three-way handshake connection establishment and connection termination?

The initiating client sends a SYN segment to request a connection, the server responds with SYN-ACK to acknowledge the client's sequence number and advertise its own, and the client completes the handshake with an ACK. This three-step exchange synchronizes sequence numbers on both sides before any data transfer begins, as specified in RFC 793.

The sequence ACK, ACK-SYN, SYN reverses the correct order and uses invalid flag combinations; a connection cannot begin with an ACK because there is no prior segment to acknowledge.

FIN, ACK-FIN, ACK describes the connection termination (teardown) sequence, not connection establishment.

This option describes an incorrect or incomplete version of the handshake that does not match the full establishment and termination process defined in RFC 793.