I have a ubislate 3g7x. It has processor MT:8312ca and 512mb ram. it gives no reaction to power button. but still whenever i connect it to my pc, COM port is detected. but i dont know what to do here? is it that my tablet is permanently dead?
Try to remember how You used to connect it before and touch the areas of touch screen that were used back when phone responded. Perhaps it is just display that went off. This might be cheked by charging - if during charging display is dead then it is dead (obv). But if it responds - problem might be in a touchscreen or the power button.
But for best solution try to take your device to a service centre.