how to Revert Samsung S9PLUS Android 10 to 9 without losing warranty - Samsung Galaxy S9+ Questions & Answers

Hello,
Begin of this year I received the android 10 update on my before good working fast Samsung S9+ phone, Nearly a year old ! Just after installing Android10 i got performance issues, and I still cant get used to the new interface. I feel it's getting worse time after time, the keyboard laggs, and the phone has became more buggy and slower.
I just want to go back to Android 9/
Because my phone is still under warranty, I would like to revert without losing warranty. I have read somewhere that if I flash with Odin, Samsung wont notice it. Unless Knox get damaged.
I came across this tuturial:
https://www.youtube.com/watch?v=CdTT4cEUWc4
Looks simple. Picking the last android 9 release which corresponds my phone and flash it with Odin V3.14.1 like in the video.
Thing I cant find out is.... which country is my phone from? I am from the Netherlands and have bought it from the company BelSimpel. But I can remember it came with some German T-Mobile carrier apps. So maybe they imported it? How can I find this out?
Also , another strange thing is that when I registered the phone with Samsung , it tells me the following:
SM-G960F/DS
SM-G960FZAHLUX
This is NOT the case. It is not a s9 but an S9PLUS
Samsung Galaxy S9+ 64GB G965(F) Duos Black is pointed in the invoice. And also shown on the phone.
{
"lightbox_close": "Close",
"lightbox_next": "Next",
"lightbox_previous": "Previous",
"lightbox_error": "The requested content cannot be loaded. Please try again later.",
"lightbox_start_slideshow": "Start slideshow",
"lightbox_stop_slideshow": "Stop slideshow",
"lightbox_full_screen": "Full screen",
"lightbox_thumbnails": "Thumbnails",
"lightbox_download": "Download",
"lightbox_share": "Share",
"lightbox_zoom": "Zoom",
"lightbox_new_window": "New window",
"lightbox_toggle_sidebar": "Toggle sidebar"
}
And last question...... when I have found out which country I need for stock android 9 (last version), where can I find this last firmwire? Sammobile does not show it for my phone.
I hope you guys can help me out! I bought the phone without a subscription to a carrier, for my carrier I just use sim-only which I frequently change when it gets cheaper elsewhere. I am very depended on the phone, dont have the money to buy a new one so I am very cautious.

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The sammobile app says the following on my s9plus
Product Code: SM2G965FZKDDTM
PDA: G965FXXU9ETF6
CSC: G965FODX9ETF6
Baseband: G965FXXU9ETF2,G965FXXU9ETF2
Bootloader: G965FXXU9ETF6
And another app says this: (strange , because I live in the Netherlands)

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Can't help you but you definitely helped me. I'm keeping my S9+ on Android 9.

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To my knowledge you cannot revert to Pie/9 without loosing warranty. Your phone is on the 965FXXU9ETF6 firmware with CSC code (region code) DTM (which by the way is for Germany).
The bootloader binary of your firmware is XXU9ETF6 is 9. Samsung has rollback prevention implemented in their firmwares which does not allow downgrade to a lower bootloader binary. The latest Pie firmware for your region is G965FXXS7CSK6, binary 7, which unfortunately makes downgrade impossible without loosing warranty.
Have you tried a full factory reset? It might solve your problems. I see that you are on OneUI 2.1, which to my experience should be pretty good. Battery is awesome. I'm on G965FXXU9ETF5 for the NEE region (Nordic) and everything is fine.
Rgds,
sten_amund

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sten_amund said:
To my knowledge you cannot revert to Pie/9 without loosing warranty. Your phone is on the 965FXXU9ETF6 firmware with CSC code (region code) DTM (which by the way is for Germany).
The bootloader binary of your firmware is XXU9ETF6 is 9. Samsung has rollback prevention implemented in their firmwares which does not allow downgrade to a lower bootloader binary. The latest Pie firmware for your region is G965FXXS7CSK6, binary 7, which unfortunately makes downgrade impossible without loosing warranty.
Have you tried a full factory reset? It might solve your problems. I see that you are on OneUI 2.1, which to my experience should be pretty good. Battery is awesome. I'm on G965FXXU9ETF5 for the NEE region (Nordic) and everything is fine.
Rgds,
sten_amund
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Good evening Sten,
Thank you for your information.
The biggest issue for me is the warranty. The Android Doctor user from youtube says: it doesn't void warranty
I don't know on what information he based this conclusion, but I am asking him and waiting for a reply.
After a bit more research I've also found this ( but not concrete how they got this info about not losing warranty)
https://www.reddit.com/r/GalaxyS9/comments/e3kp9f/downgrade_s9_android_10_to_9/
there's no way for your warranty to expire unless Knox is tripped. Therefore your warranty should not be voided unless you make a mistake
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Doubt you'll ruin the warranty unless you trip Knox. Use Odin and you'll need a firmware with the same boot loader. However I have had a S8 get bricked by Samsung and their beta program. Good luck
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Short answer, reflash official Pie Rom with odin. You can flash official Rom with odin million times with no problem. Note: you can always flash the official Android 10 ROM for your country later when it got released. No warranty problem at all.
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Click to collapse
Also, when I check the firmwires. I See the latest PHN firmwire for Netherlands is (G965FOXM7CSJ5)
This?: https://sfirmware.com/downloads-file/113514/SM-G965F_1_20191107153840_9ac3z2kgrl_fac
https://sfirmware.com/android-9-pie/
EDIT:
I have an answer from Android Doctor:
I didn't have a problem downgrading ,however it has been sometime since I downgraded back to Android 9.0 so there's been many Android 10 security updates and patches that probably now prevent the Downgrade,however u should be able to first Downgrade to the earliest Android 10 firmware resulting in it removing any Downgrade prevention patches then after that try the Downgrade back to the latest Android 9.0
What do you think about this?

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There is no way you can remove the downgrade prevention as far as I know unless you downgrade to a version with the same bootloader binary. Someone in this forum with more experience might have other information (I'm no expert). You are already on Android 10, OneUI 2.1, with bootloader binary 9, and you cannot revert back the regular Odin way to the first release of Android 10, OneUI 2.0, which has bootloader binary 7. Odin will simply prevent that because of mismatch in bootloader binary version.
It is correct, though, that you can flash an official firmware how many times you like without triggering Knox - but again that requires the same bootloader binary to work.

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You need to use TWRP to flash old .imgs because its already updated bootloader

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Ok guys. Its still under one year warranty from Samsung. Ive traveled 300km to a repair center but they ended up just updating the system software and say there is nothing wrong with the phone. I swear it is so terrible slow that it really pisses me off!
I have nearly used it for a year. Maybe I should sell it, and go for another brand since Samsung has screwed me many times before. Does anyone know if the Pixel 5 is a good phone? Though I heard they will use samsung chips.
At the repair centre they also said it is impossible to revert back to android 9. Is this true? Such a pity, I liked the s9+ very much on android 9 and have bought lots of accesoires.

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I'd try flashing stock with Odin to COMPLETELY wipe the phone, not just a simple factory reset from settings or recovery. Maybe it'll fix all your performance issues. Make sure to backup everything correctly.

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ShaDisNX255 said:
I'd try flashing stock with Odin to COMPLETELY wipe the phone, not just a simple factory reset from settings or recovery. Maybe it'll fix all your performance issues. Make sure to backup everything correctly.
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They already did twice at the samsung repair centre...... did not help anything unfortunately So sad....