[Verizon Galaxy Note 4 General] newuser134:
A very good question -

A year ago I bought the Verizon Note 3 dev ed used from someone on eBay, I know it doesn't directly concern the Note 4, but I am planning to get a Note 4 dev ed soon, and it is the same scenario, so bear with me :) , the original owner had flashed some after market roms and kernels, and I wanted to return to bone stock the way it came from Samsung to try a few things to help with the retail edition unlock and a few other things. The stock files were nowhere to be found, and the original owner had not made a backup when the phone was stock. A few devs here on xda had some close to stock but still somewhat custom restore files for the dev edition, but those were not the same ones that came with the phone factory stock, including the stock recovery. At the time when my phone was new, it came with build # MJ3 kernel, modem, recovery, system and cache partitions, we'll disregard aboot because that is phone-specific when it comes to dev edition, and you can't really get it from anyone else, so that was luckily stock as it should be. At the time I got the phone, the first batch of retail phones had build number MI9, and were being updated to MJ7 and MJE. Even though I wanted to try to do a few things with the stock dev ed modem (MJ3), I could not find it. Obviously I could get the MJ7 or MJE from the retail version, and it would work, but even so, it would be a frankenstein with MJ3 aboot, MJE modem and recovery, MJE system and kernel, etc.... Even though the stock recovery from a retail version may be the same, the recovery image from different build numbers may NOT be the same, even if both are from a retail or dev edition phone. Sometimes one needs to get the EXACT version that came with their phone initially, as we have seen how newer build numbers do not allow downgrading to older build numbers on retail versions, and sometimes older build files have exploits that newer ones don't. So long story short, regardless of there being a "good" reason, it is sometimes necessary to keep an exact copy of a file in the version that came on the phone, not from someone else's or a newer phone, you never know if you might need it later. The only way to be sure it is the exact file that was on it, is to get it from that specific phone when it's brand new. That is where this catch 22 problem occurs :) . To avoid this problem, I have decided to buy a brand new dev edition Note 4 this time, and not a used one like my older Note 3. Even to this day I still haven't been able to get a copy of the original Note 3 MJ3 system partition, I can get the MJE, and albeit it may work fine, it is not the original system files that came on the phone new.

On the Note 3 dev edition, it was possible to root without installing a custom recovery first, same on the Galaxy S3 even before the bootloader was unlocked, either by installing a file on sd then calling a script to get root, or by flashing an already rooted /system image from Odin. I'm pretty sure that can probably eventually be accomplished on Note 4 as well. At the very least, by using 2 phones with the same firmware and build numbers, one can install custom recovery on one of them, make backup of stock unrooted system partition, then root with "root.zip" flashable file and use cygwin to make an Odin-flashable tar from the system.ext4 backup file to use to gain root on the other phone without custom recovery, then the 2nd phone can get root without custom recovery and make backup of the stock recovery. I'm sure the devs that offer stock recovery files probably did something similar to get it, but there is no guarantee they have the same build number (currently NI1 in the case of the Note 4) when updated versions come out later and you need your original build files, I hope you see where I'm going with this.

For this reason, I have been trying to figure out and make a point of getting the first batch and make a backup of everything immediately. One can always update to a later version, but finding the files to downgrade may not always be very easy. A good example showing the point of this is making a backup of your dev ed aboot partition right away. If it gets messed up and you need it later, no one can help with that. The recovery partition may not be as picky, but one never knows what exact file will be needed later that may not have been backed up initially. Therefore I have come to the conclusion it is the best thing to make your own backups of the very stock files before doing anything else. Hope that makes some sense.