Why WiFi is turned off automatically after I switch input sources on RP02
It's because all USB 3.0 ports (include Front USB 3.0 (Picture 1, No.5) and Side USB 3.0 (Picture 2, No.6)) will follow the current input source on the board.
ex: If you switch the input source to HDMI, the USB 3.0 port will also switch to HDMI, that's why you plug Wi-Fi dongle into USB 3.0 port, the Android turns Wifi off because the USB 3.0 port switched to HDMI.
Picture 1. The front panel of RP02
Picture 2. The side I/O ports of RP02
The USB port Side USB 2.0(Picture 2, No.5) and Back with a cover USB 2.0 port(Picture 3, No.17) won't follow the input source, so we suggest using Side USB 2.0 for the remote dongle(Picture 4), Back with a cover USB 2.0 port(Picture 3, No.17) for the Wi-Fi dongle, it's by HW design.
Picture 3. The WiFi dongle USB port of RP02
Picture 4. The remote dongle USB port of RP02