Restart=on-abort in systemd will service autostart when server is restarted? Given I cannot test it by restarting the production server, if the service is set to `Restart=on-abort`, will it start automatically after I restarted the server?

The `Restart` setting is not related to the initial starting of the service at all. The service is started if it is enabled (see `systemctl status servicename`) or if it is required by another service which is started.