In my case, the main switch is on. When the PC is switched off, all HDDs automatically go to standby. When the PC starts up again, all HDDs that were previously in operation also start up again automatically. However, HDDs that were switched off manually remain in standby.

This depends on whether the main switch on the back of the device is on or off. As long as the switch is on, the drives remain in standby mode, even if the computer has been switched on and off again in the meantime. If the main switch is switched from off to on, each drive must be activated individually on the front of the device.

There's a main switch at the back and a disc switch at the front, so you have to turn everything on to use the computer disc when it's off or on.

Yes, you have to switch them on individually