Yes indeed. As it says in the manual: "The zero in these commands can be changed to any digit from 0 to 8, being the number of the machine to which the command is addressed".
The MNCHGC<m>497 command is equivalent to turning off the switch at the bottom of inverter <m>, and the MNCHGC<m>498 command is equivalent to turning it back on again, with two qualifications:
1. The physical switch must be on.
2. An inverter will never power off completely, after the serial command, as it will when the physical switch is off and there is no incoming AC or PV.
No. That would need to be done by external software. Such software could easily be created using the Node-Red visual programming tool running on a Raspberry Pi or Beaglebone-Black and communicating with any one of the inverters. @Monkeytom suggests setting the threshold for telling the next inverter to connect to the loads, at about 60% load (as reported by a QPIGS or QPGS<m> command), then leaving it for half an hour after the most recent drop below the same power level, before putting that inverter back in standby mode.What happens with paralleled units if the load goes up will the standbys come back on?