You don’t need to backup anything if you have no content on the phone you care about, like pictures or other documents.
Those will be gone after flashing.
If you do have something like that, copy it somehere, like your PC, or a cloud storage or similar.
Ahhh okay… the directions made it seem like this was something that had to be done. This is a fresh phone out of the box.
If something goes wrong is there a way with out a backup to restore the phone back or once the process happens its all but broken?
Have a look here:
I flashed my phone 4 times until it run SF. I used Emma in a VBox to flash Android again after a failed flash. That worked flawless and easy.
The reason why it failed was obviously, that the SW binaries were too large, to flash them at once so I limited the package size with the Option -S 256M and flashed the binaries separately. (maybe that’s due to my fastboot version, but I don’t really know),
The procedure itself is very simple and there shouldn’t be too much that can go wrong. I have flashed so many phones and never bricked one of them. Even when there were sometimes smaller problems a reflash was always possible.
Where to get latest SFOS for Xperia 10 mark III? sailfish-os-torrents/4.5.0.19 at main · black-sheep-dev/sailfish-os-torrents · GitHub torrent seeds is inactive
Really useful 
I wanted to recover to my local disk rather than the SD card so:
ssh root@10.42.66.66 dd if=/dev/sda79 bs=4M | pv -rab > sfos_backup_sda79.img
Worked for me and got 35MiB/s
Note that you need to set the root passwd in a plain shell before starting sshd as that’s not actually set to ‘recovery’
OK so I cannot get mobile data on a 10iii with Vodaphone in the UK 
My device was upgraded to 13 62.2.A.0.533 and when flashed it worked just fine with everything except mobile data.
I tried the SW 11_4.19_v9a and 12_4.19_v2a and both worked to the same degree (v3a doesn’t even give wifi - olf you have a PR for the docs with the right link now 
)
I used Emma to get to 62.0.A.3.109 (that would not OTA though) and again tried both SW variants - nope.
I used the Xperia Companion to get to 62.1.A.0.675 and both SW variants… nothing.
So if anyone has any ideas I’d like to avoid having to buy an Xperia 10ii
Oh, sorry, I will gladly revise my documentation to improve it. Unfortunately I see no PR yet, but maybe I am looking at the wrong place.
BTW, @wetab73 documented that using the SW_binaries_for_Xperia_Android_12_4.19_v3a_lena.zip (or later releases of Sony’s software binaries for AOSP for the Xperia 10 III) with an SailfishOS flashed on an Android 12 or 13 base results in no working WiFi and mobile data.
P.S.: As many have their Xperia 10 III’s running acceptably (at least WiFi), one may consider other reasons.
@olf : Fix link to lena v2 binaries (!3) · Merge requests · olf (Olf0) (Olf0) / SailfishX on Xperias · GitLab
Yes, I saw that post - the link seemed to go to the v3a in my case - hence the MR.
Sadly neither the v2a version nor the earlier v9a give me mobile data
Thank you very much: Merged.
I wonder why I missed that, both the PR and the incorrect link in the first place when I searched for it, which (without a version identifier) pointed to the SONY binaries for lena Android 12 “latest” (which still is v3a).
So would it be correct to reiterate for anybody who’s gonna start doing this from scratch, that it seems that the right combination is the following?
Android 13
SW_binaries_for_Xperia_Android_11_4.19_v9a_lena.img
Yes - but beware that I could not get any of these to use mobile data (or 4G) with Vodafone in the UK
Eventually I returned my Xperia 10iii and bought another 10ii
And guess what - that didn’t work either (still doesn’t)
My old 10ii (like 2021 old) with a broken screen works just fine with mobile data and 4G
Clearly it works for others so it could be a UK or even Vodafone specific issue.
APTOID I don’t understand Aptoid installs itself after each reboot
I tried to install Sailfish over android 13. I put SW_binaries_for_Xperia_Android_13_5.4_v2a_murray.img on same folder where Sailfish files are. Executed command sudo ./flash.sh. Installer wants androi 11 binaries.
The supported Sony Vendor partition image wasn’t found in the current directory.
Please download it from
Ensure you download the supported version of the image found under:
“Software binaries for AOSP Android 11.0 - Kernel 4.19 - Lena”
and unzip it into this directory.
What can I do?
Do what it says.
What you are installing over has no relation to what binaries to use.
If My Sony Xperia 10 III have Android 12, so what software binaries should be installed “SW_binaries_for_Xperia_Android_11_4.19_v9a_lena.img”
or
“SW_binaries_for_Xperia_Android_12_4.19_v3a_lena.img” for SailFishOS 4.6.0.15?
As @attah mentioned above, it does not matter. You can flash any binaries you wish afterwards anyway, at any point, without affecting your data/setup.
Note that by flashing “SW_binaries_for_Xperia_Android_12_4.19_v3a_lena.img”, you 'll end up without WiFi and Mobile comms.
Android 12 v2a works OK, but camera does not work in AppSupport (if you do not use any android camera app, it does not affect you).
I, personally, flashed SailfishOS on top of Android 12 latest firmware, together with Android 11 v9a binaries. Up to now, everything seems to be in order…
thank you very much. I installed “SW_binaries_for_Xperia_Android_11_4.19_v9a_lena.img”