Galaxy Note 2, I think is the best ever Android Smartphone from Samsung. Today Samsung have releases the latest firmware for Galaxy Note 2 in India Region. If your Galaxy Note 2 is running custom ROM or was rooted, then may be you cant get the update notification on your phones. So, you need to unroot your phone or download the firmware file and manually flash into your Galaxy Note 2 via Odin.
Here is the step by step tutorial on how to download Galaxy Note 2 N7100 Android 4.1.2 N7100XXDMB2 firmware and flash via Odin. Before start, please note that manually flash firmware into Android phones may void the phones warranty and has the risk that cause your phone brick. Do not unplug the USB connection from PC during the firmware flashing process. Tutorial below is only for your reference and do it on your own risk.
Step 1: Download Android 4.1.2 N7100XXDMB2-1359939157.zip, then unzip the file. You will get N7100XXDMB2-1359939157.md5 .
Step 2: On your computer- desktop or laptop, Open Odin 3.04 (Download Odin).
Step 3: Go to settings > Developer Options to enable your phone debugging Mode. Then turn off your phone and then turn your phone in download mode by press (Home+power+vol down) button.
Step 4: Connect phone to the computer and wait until you get a yellow sign in Odin.
Step 5: Add Android 4.1.2 N7100XXDMB2-1359939157.md5 to PDA.
Step 6: Start flash, sit back and wait a few minutes.
Step 7: Galaxy Note 2 N7100 will automatically reboot once installation complete.