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When the tablet is stuck in Meta Mode it indicates a fault with the firmware.
You'll need to reinstall the firmware using a flash tool.
You can find the firmware on Lenovo's Russian website:
Also see this guide: https://aluk4rd.wordpress.com/2014/09/08/an-easy-guide-for-restoring-your-stock-4-2-2-firmware-on-your-lenovo-yoga-tablets-8-and-10-b6000-and-b8000/