Quote:

The latest N910VVRU 2BOF1 bootloader is incremented; i.e., if you take the OTA or flash the official firmware via Odin, you won't be able to downgrade.



Quote: For Retail Edition: This is very important if you want to gain ROOT access when available & keep it over OTAs then.



For Developer Edition: If the bootloader is incremented with any coming OTA, it'll block your unlocked bootloader for good & you'll end up with a Retail Edition.

Safe upgrade allows you to downgrade (roll back) to any previous firmware (KK or LP)...

Check this thread for more details!