Select your exact hardware version from the dropdown menu. For this specific model, select or V3.20 (depending on how it is displayed in your local region).
A: No. Firmware is hardware-specific. The V3.20 and V4 have different internal chipsets and will not be compatible. Installing V4 firmware on a V3.20 will brick the device.
Never flash firmware over Wi-Fi. Connect your PC directly to one of the router’s yellow LAN ports using an Ethernet cable.