hello, I’d like to ask again a question I’ve already asked elsewhere on the forum. But after reading a lot of documentation and trying a lot of things, I still can’t figure it out. So I’ll try to put my question clearly.
My Cmf 1 is under Nothing 3.0 Android 15. I received it under android 14 Nothing 2.6, but it immediately made me apply updates that brought me to TETRIS-V3.0-250208-2015.
Although some say they have successfully installed /e/OS Android 14 almost all messages say that it is not to be done and that you have to downgrade to Android 14 before installing /e/OS.
Actually I tried the easy installer and it didn’t worked. So I decided I have to rollback to Android 14 first.
In Install e/OS on CMF phone 1 Piero gives a link to spike0en’s github repository where there are lots of explanations (thanks ). In this repository there are 3 kinds of files for each version: incremental OTA, full OTA and OTA images.
I tried to use the Nothing Offline OTA Updater with the incremental OTA Tetris_U2.6-241204-2338. I got the error: “error code -2: pre-build-incremental is different from ro.build.utc”.
My question is:
did I use the wrong file (should I use a file from the 3rd column OTA image?)
or should I proceed in several steps via TETRIS-V3.0-250208-2015 → Tetris_V3.0-250111-2249 → Tetris_U2.6-241204-233?
I hope someone can help me, I’d really like to be able to switch to /e/OS (without bricking my phone )
Without me knowing the device … An incremental update requires a strictly defined previous version and only applies the necessary changes to this base to get to a new version.
Yes. You had an Android 15 version as a base and tried to apply the necessary changes which should get a previous Android 14 version to a newer Android 14 version. This must fail.
For the full OTA it is explicitely written in the spike0en github " Full OTA cannot be used to downgrade — it can only update to the same or a higher build."
So I think to myself I can’t use it , am I wrong ?
It is also written :
“Stock OTA Images – Provides unmodified OTA images utilizing AOSP’s OTA extraction tool that allows extracting incremental OTA updates, thus enabling upgrades, downgrades, and partition flashing when full firmware packages are unavailable.”
Does it means that to rollback to android 14 I have to download OTA images (the 3rd column) ? But in this case there are a lot of files, should I dowload all of them ans use fastboot ? And I m not sure of the difference with a full OTA ?
Another thing is that it is written to “Backing Up Essential Partitions”, but for that you need to root the smartphone which is another thing I don’t know how to do , sorry
I do not know the device. There is a general rule in Android, “Never go back”.
Just to help you rule things out, I would say that an Over The Air update must be safe to perform, so it should throw an error if it is being used for anything which is a downgrade.
Most devices where you want to downgrade, you are going to be looking for an expert or even “engineer’s” solution, that is rather than an Upgrade operation carried out in user space such as Recovery and I would say (most) adb operations.
Generally one would search for a Fastboot ROM specified or recommended to carry out the intended downgrade.
Many users having accepted an upgrade just wait for /e/OS to catch up to that Android version.
Thanks a lot, that’s a clear, explicit and wise answer Since I don’t want to get in too much trouble with my smartphone I will wait until the /e/OS android 15 … does anyone have a date for this version ?
Thank you !
Hi, @cedric.vdd,
as mentionned in another thread here, I looked at XDA and asked for confirmation.
It is possible to install /e/os 2.9 on CMF phone 1 running Android 15.
I did it myself and it went smoothly.
Thanks for all your answers …
One last (or maybe not ) question : in another post, Piero you told me " be carrefull about the Android Security Update release date included in the new build not older than the one already installed is still valuable advising…". My Android security update is 1 April 2015 . Where could I find this information on the /e/OS dépôt to check ? Because I see 20250321 in the name I image it is a march version, so maybe it can’t have this security update ? And then is it a big problem ?
Have a nice sunday
In your running NothingOS you should look in Setting > About phone > Android version … here it can vary by manufacturer … you will be looking specifically for “Android SPL”.
oups ! sorry ! I read it twice and see 2025 …I could say that’s because it’s difficult for me to write in english (wich it is), but actually I just made a mistake
But do you think this problem is big (install a march security patch on a april security patch), or am I too cautious because as you said before /e/OS is a fastboot ROM and could be use to downgrade ?
I do not know … anything I write is hypothetical, by which I mean, I never tried it myself … it has not been said previously that there is any anti rollback hazard on this phone.
Downgrade of Android version and rollback of Android SPL are handled differently within Android, and again differently by different manufacturers.
Google provides instructions for their Pixel devices and providing you follow their Fastboot instructions no hazard is mentioned – Edit, except the Pixel 6 series where a particular warning exists reference Android 13 → Android 12.
Samsung publishes codes and a certain “reversal” just won’t work.
On this forum we see the consequences of tripping anti-rollback on Fairphone where the device is bricked. In this case the hazard is published as device specific.
For tetris I have not read “anti-rollback” warnings.
Thanks a lot to everybody ! I did it and it works easily !!! It is so wonderful, I a NOW on a cmf1 on /e/OS using telecoop (wich is a french phone operator “coopératif”) … C’est trop bien, merci à tous !
). In this repository there are 3 kinds of files for each version: incremental OTA, full OTA and OTA images.
Since I don’t want to get in too much trouble with my smartphone I will wait until the /e/OS android 15 … does anyone have a date for this version 
