Chosen Solution
Whenever I plugin my charger, within a minute it shows battery full; if I unplug the charger it discharges rapidly and if I restart the device it shows low battery. Why it is happening like this? How to overcome?
You should probably start by replacing the battery. Here’s for example a seller who will ship you the tools and instructions, and let you return them in case it turns out not to be the battery. Please note that I’m not vouching for anyone/brand, it’s just a suggestion as to the types of solutions that you can find if you search for something like “battery replacement Samsung Tab 2.0”