What is the Voltage on a tablet's battery when it is turned off
Those 3.7 V batteries need to have a voltage between 2.5 V and 4.5 V per cell, if they're outside that range then consider them to be damaged. Some cells might survive a short time below 2.5 V. But 0.1 V means that they're dead.

9 V might be on the edge of what a device that is supposed to work on 2 Lithium based cells in series can handle. Chances are that a 9 V battery is unable to deliver enough current to start the tablet. So the tablet will attempt to start but as soon as it switches on any part which consumes a lot of current (for example the backlight) the voltage will drop (due to the high internal resistance of a 9 V battery) and the device will reset.