Download Android 4.1.1 Jelly Bean stock firmware for Onda V812 tablet from here or from here. Download latest Android 4.2.2 Jelly Bean stock firmware for Onda V812 tablet from here. Download another Onda firmware from here.
Archive name: A31_sun6i_android_fiber-onda809q9_20130711_V2.0_240
Archive file size: 193 MB
Support: Allwinner A31
Model: Onda V812 tablet
FW version: Dongel_20130708
Pixels: 800 x 480
Build number: fiber_onda809q9-eng 4.1.1 MASTER 20130711 test-keys
Caution: Please do not update firmware unless you know what you are doing, you really want it or it is absolutely necessary. Firmware updates may occasionally have bad results, like bricking your device, temporarily or permanently. The firmware update process is done entirely at your own risk. Before attempting to update the firmware, back up your data.