copypaste from an earlier email: If you have a tablet now, the goal is to overwrite the existing image with a compatible image. Maintain compatiblity with whatever system works.
Each tablet includes the following base hardware Touchscreen Front Camera Back Camera Audio speaker Microphone 512MB memory ~4GB flash storage Graphics (mali400)
The tablets [if they are all the same] have the Allwinner A13 'sun4i' processor in them.
The device and packaging has no markings or branding to identify it. The PCB has a silkscreen inscription: 'TW_A0910_16B_V1.1_0830' and date '2013_08_30'. The id tag is searchable as "TW_A0910" as well, and more searches and reading might provide more insight.
This GUI based [LiveSuit, see below] flash process works, but its a pain to go through roms blindly one by one. I believe the key improvement would be to get the UART to interrupt the boot process, watch it, and have a better chance to match software images or build images from scratch for the hardware. The UART might be available as USB OTG via the microUSB port, or multiplexed in via the SD card.
Links: Factory Flashing software (Linux, OSX, Win) for flashing tablets: LiveSuit, or 'PhoenixSuit' (which may be Windows only) http://linux-sunxi.org/LiveSuit https://github.com/linux-sunxi/sunxi-livesuite
http://wiki.openwrt.org/doc/hardware/soc/soc.allwinner.sunxi#installation.process Rundown of various devices with allwinner sunxi processors and differing hardware. The best part is at the end where the multiple boot process (boot0, boot1, 'FEX', 'u-boot', rootfs)
http://www.techknow.me/forum/index.php?topic=4499.0 Overwhelming list of 'ROMS' for cheap clone tablets behind a registration-walled forum. One of many such forums.