So that I can utilize some of the advanced features of my Deco X55 and older Deco X20 models, I need to update to the latest firmware.  But first I need to know the hardware version to ensure that I am downloading the correct firmware from the TP-Link site.  The link "How to find the hardware version on a TP-Link device" did not help me because the label on the bottom of my X55 does not specifically mention a version.  It does have US/1.26 on the upper right hand corner of the S/N barcode, which led me to believe that it is version 1.26.  Because there are three firmware versions of the X55 model (1, 1.26, and 1.60), this seems accurate.  Then I went to download the firmware for my X20 model, which also has the same US/1.26 in the upper right hand corner of the S/N barcode.  But the only firmware versions available for that model are 1, 1.20, 2, 2.6, 3, 3.6, 4, and 4.6.  So before I proceed to flash my X55 with the version 1.26 firmware, could someone from TP-Link please assist me in confirming the version number for both of my units?

Also, I compared the downloads for the instructions and firmware for each of the the Deco X55 versions to see if I could figure this out on my own, but that just confused me even more.  It appears that you might have the incorrect files uploaded to the versions.  For instance, version 1 and 1.60 both have the same 1.26 user guide, but version 1.26 does not have this file at all.  The zipped firmware for version 1 is labeled Deco_X55_V1_1.2.5_20230511, which is identical to the one in version 1.60.  That is understandable if that is the same firmware, but it might be less confusing to users if you label it as V1.6.  The inconsistencies in the pdf documentation that has been uploaded to each version does not instill much confidence in me selecting the correct firmware that does not brick my routers.

Deco X55
Hardware version? US/1.26
Firmware version: 1.0.1 Build 20221103 Rel. 43293

Deco X20
Hardware version? US/1.26
Firmware version: 1.5.1 Build 20210204 Rel. 50738

Ultimately, what I am attempting to do is allow some of the units to connect to units other than the main one, instead of having them all connect to the main one, as it is set up by default.  My residence has concrete walls that do not allow Wi-Fi signals to pass through, requiring me to connect a "trail" of mesh router nodes from the internet/router entry point and extend throughout my place.

Thank you for any assistance you can provide.