1 if the grid goes down my PV shuts down as it need to know the Hz of the mains to feed to it.
2 If you add batteries & store power I understood you would not get the Feed in Tariff payment from the energy provider.
1 My PV only stops when the sun don't shine.
2 If the battery is AC coupled, you don't lose FiT.
I have an additional battery inverter.