Unrooting the Galaxy S3!

I have two phones. One for personal use and one for my project; both Samsung Galaxy S3. My personal phone is updated to version 4.4.2. My project pone was at version 4.1.
This let me know that my 4.1 phone could be updated to 4.4.2, which is needed since the Sensor Tag only works with Android versions 4.3 or later.
However, I forgot to update my project phone. And so, when rooting my project phone (which I posted about earlier), I flashed a ROM for 4.4.2 instead of 4.1. This was not good as rooting needs ROMs that are meant for your specific version type. A warning for rooting phones is that you might not be able to get firmware updates. Thus, I wasn't able to update the version of phone, which was needed since Sensor Tag can only work with versions 4.3 and higher on Android.

So here is a How to Unroot the Galaxy S3 Guide! :)
Guide link
^this guide is really easy to follow, so I'll just direct you over to it. Lots of pictures!!
It also provides the complete stock file for the Samsung Galaxy S3, so no need to go searching for it! Yay :-)

However, unlike the previous How-To I wrote for rooting a phone, this How-To uses Heimdall instead of Odin. I couldn't really find any guide easy to follow for unrooting with Odin (if you know one, please feel free to share!).

I unrooted my phone in order to unbrick it, updated the version, and then re-followed the instructions to root it again. Now, my phone is rooted and working properly!