RealNeil

You should never feed back into the grid without prior authorisation/registration/certification with your local municipality or Eskom. It's just not legal. Even if your inverter is capable. They will give you a new power meter because if you have the wrong prepaid meter it can even cost you money for every bit of power you are giving away.
The Deye inverter has got anti-islanding protection built in. Any inverter that has a grid-tie function has to be, in order to comply with code/regulations. It just means that the moment the grid is off, the inverter will no longer export any power into the grid, it will automatically immediately shut off the non-essential supply and stop any exporting the moment it picks up that Eskom is down.
In that way nobody gets hurt who is working on the power lines while Eskom is off. It works different than if you've say got a generator that you hook up to the grid while Eskom is off, there you could hurt people and be in trouble.
But the Deye never can do that. You don't even have to set anything special up as long as the inverter is installed correctly.
What you call "Single Island Mode" is actually "SIGNAL Island Mode" which is to activate a relay for a function that is different to what you are asking right now.