[Samsung Galaxy S 5 Unified Development] FNetV1:
I just installed this on my G900P kltespr Sprint Galaxy S5. The app installed without any problems. I was able to add a slot without any problems, I rebooted and EFIDroid showed up, I selected TWRP and then selected the new rom's slot (I called it Exodus_Marshmallow) and a pop up came indicating in was entering there, after about 10 seconds TWRP started loading and loaded just fine.

I went to wipe>advance> and wiped system, cache, internal storage, but did not wipe /data /efs /...and all the others.

I went to my Micro SD card and proceeded to install the Exodus Marshmallow AOSP rom, it installed just fine and quikly, then I installed the full openGAPPS for Marshmallow, the installation went fine.

After that, I rebooted the phone, the EFIDroid menu came up, I selected to start Exodus_Marshmallow and the Google AOSP (fan styled spinning four sticks in the center of the screen) boot screen started showing in animation. After waiting like an hour and still the boot logo showing and not progressing I knew something wasn't right (on the first boot it didn't take more than 5 to 10 minutes to boot when I had it installed normally like a few weeks ago).

I restarted the phone and selected to load my internal stock rom (the TouchWiz lollipop rom that came pre-installed with the device), the "SAMSUNG" boot screen with the dual star like "splashes" animation started displaying in perpetual cycle, again, just like in the other rom, the stock rom never booted, I let it sit for a really long time, it never went passed the "Samsung" boot logo screen.

What I know: the phone never "froze" as the boot screen always kept playing its graphical animated logo all the time.

To fix the situation and get out of the problem that it never booted to any OS including the device's stock rom, I had to ODIN TWRP from scratch which got rid of EFIDroid then I was able to enter TWRP normally by pressing PWR+HOME+VOL UP, and then I restored just the /boot partition from my stock NANDROID backup. after this I rebooted the phone, my stock OS loaded up really quick like always and was able to have normal access and functionality again.

I tried it twice.

I gave it another go: I installed the EFIDroid app, went to install and clicked on "repair" after like 30 seconds of checking for updates it installed, I erased my previously created slot, re-created it, rebooted the phone, installed the same AOSP/CM based ROM and experienced the same exact issue and had to do the same back off as I originally did which was restoring original TWRP by ODIN flashing it, flashing backed up /boot from nandroid and then stock was able to boot just fine.

* Thinking that I possibly created some unknown issue by formatting partitions not explicitly mentioned on the OP since OP only said to format /system and thats it before installing the new rom on the alt slot, I went ahead and installed EFIDroid by the third time, this time when EFIDroid showed up upon restart I just selected to boot the internal stock rom, and I got the same exact issue, the stock SAMSUNG boot logo showed on and never proceeded after that, stood there forever. Once again I had to back off and get rid of EFIDroid to once again be able to use the phone.

question:

Someone here said that EFIDroid currently doesn't work on kltevzw which I take it its the Verizon Wireless variation of the Galaxy S5, (judgin by "vzw") since my kltespr is the Sprint variation of the Galaxy S5 and both device being CDMA based, could it be that EFIDroid doesn't work on the kltespr / G900P variation?

Android Version of my Stock ROM: Lollipop 5.x

Current Baseband: G900PVPU1BOA6

Do I have plan to upgrade the stock rom to Marshmallow? (in case if MM is a requirement):

1. No, I need access to certain features which I can at the moment find only on Lollipop such as being able to change PRL's at will to my chosen PRL (can force roaming when I visit my friend in a suburban where phone picks up a weak sprint signal that has no data/voice but I can roam at full bars under Verizon being of course careful not to consume too much data, but mainly to be able to receive/make calls when I am there)

2. My work requires the use of a proprietary app that only works on Android and lower versions of Android (eg. Kitkat) there isn't any plans to update that to work under Marshmallow, so because of this additional reason I am stuck with Lollipop at the moment.

With that said, I hope that Marshmallow isn't a requirement for EFIDroid to work properly just like (unfortunately for me) it is a requirement for MultiROM to work under my device (I learned the hard way, I installed MultiROM two days ago only to find out that I wasn't able to get the boot menu to show up or my slot/ROM to boot only after doing additional googling to came accross some FAQ that mentioned I needed Marshmallow installed first. Problem with Marshmallow is that I read that it locks your bootloader and thus would probably disable the ability to downgrade to an earlier rom (correct me if I am wrong)

Now, I am happy to run Marshmallow in a multiboot environment where I get to keep my original Lollipop primary rom intact when I need it for work and for those eventuality I need to force my phone to roam and I dont want to have to do restoration of Nandroid backups to switch beween roms because each time that I have to restore a nandroid I am writting well over 2 GB of data to my internal NAND flash which would eventually wear it out.