Android is built base on the open source OS – Linux. Rooting and manually flashing any ROM via odin will void your service provider warranty, but , as developer, i have always flash and test custom ROM on my Android devices especially Samsung Galaxy S3 and Galaxy Note 2. To flash custom on Samsung Galaxy S3 and Galaxy Note 2 is a very simple as you only need to know the basic steps on How to Root , How to Backup , and How to Wipe. But after change to new custom ROM, sometime you may found that the custom ROM features may not fulfill as what you have expected and want revert back to the official firmware. So how?
If your rooted galaxy Note 2 has a proper backup, then you can revert back to the previous installed firmware on the CWM Recovery Mode . Otherwise, you need to manually download the Galaxy Note 2 firmware and flash into your Galaxy Note 2 via Odin. Flash new official firmware via Odin not is a big issues, but you need to make sure that downloaded firmware is really meet your region and your galaxy Note 2 model firmware. You can flash and use other region or different firmware baseband, but don’t flash firmware to unsupported Galaxy Note 2 Model. So, here is info on how to check your Galaxy Note Model number, your region Baseband Version, Build Number, and then flash into Galaxy Note 2:
To check Galaxy Note 2 Model Number:
On your Galaxy note 2, go to Settings >About Devices. Example here is GT N7100.
To Check Galaxy Note 2 Baseband Version and Build Number:
On your Galaxy note 2, go to Settings >About Devices. Example here is GT N7100 with the firmware- Baseband: N7100DXALI9 and Build Number: JR003C.N7100XXALIE.
On your Galaxy note 2 keypad, then tap *#1234#. Then you will get your firmware info: AP, CP and CSC version.
Go to the site Fuz.nanzen.se, click and choose on you Galaxy Note 2 Model Number. Example GT N7100.
Compare to method 1 and 2, method 3 allow to to check the latest firmware that available for your Galaxy Note 2.
After you get your Galaxy Note 2 complete firmware as above, then you can start download the firmware. You can Google search and download the firmware (example: Download N7100OLBALJ3 firmware). But, for better download source link, I always use Check Fuse Downloader application (Developer Download Link) to download my Galaxy Note 2 official firmware. To use check Fuse Downloader:
Step 1: Open Check Fuse Downloader application.
Step 2: Fill in and choose the info firmware, Model and region.
Step 3: Click the check firmware button to start download the latest official firmware for your Galaxy Note 2.