Can you please mention where did you see this, so that we could rectify it.
How old is your board? I am pretty sure all boards are shipped with Ubuntu 16.04. Are you sure you have Nvidia TX2 and not TK1 or other boards.
You are completely confused between upgrading OS and upgrading kernel. Using that approach would only upgrade your kernel but not your OS.
Nevertheless, please make sure that you indeed have Nvidia TX2 which is running Ubuntu14.04, because most likely it would be running Ubuntu16.04. But in case you are right, please flash your board using Jetpack-3.1. If you follow their instructions correctly, i don’t think it would brick. Link to Nvidia Jetpack.