Can Eth0/Mgmt port used as service port ?

No, Eth0 can only used as mgmt port, can't used as service port for traffic forwarding.

The MGMT interface is separated from the forwarding plane inside the device, and is not involved in functions of the forwarding plane and control plane.

In other words, the communication on the MGMT interface is separated from service communication running on the device, that is, the MGMT interface implements "out-of-band communication".