No AREDN Flashing for New hAP ac lite ?

I bought two  hAP ac lite  units from Amazon on 2023-12-27.  ID: RB952U1-5ac2nD-US.  Router OS was v6.49.8, but I upgraded them to RouterOS v6.49.11.  The  RouterBOARD  current firmware is v6.49.11 (factory v6.49.7).  There was some weirdness with passwords, but that seems to have settled down.  I have been working without success for several days to upload AREDN into these nodes following the AREDN first-install instructions. 

The RouterBOARD Settings (WebFig | System | RouterBOARD | Settings) page in RouterOS v6.49.11 does not have a cell to edit Reformat Hold Button time as required in the AREDN instructions (apparently using RouterOS 6.45.8), which seem to want three minutes (00:03:00).  The default value is only 20 seconds.  Is the 20 seconds time going to prevent the hAP from completing the download process of AREDN firmware?

The Boot Device on the RouterBOARD Settings window has a default value of “nand-if-fail-then ethernet.”  The AREDN instructions say to edit this (use drop down list) to “try-ethernet-once-then-nand.”  Then deselect Force Backup Booter.  Then click Apply.  Then click OK.  I have found that the Boot Device setting of “try-ethernet-once...” does not survive a power cycle of the hAP, but the Force Backup Booter setting does.  Could this impact the power-off/hold-Reset/power-on attempt to upload AREDN? 

I get the impression from some previous posts that it is not possible to load AREDN onto later versions of RouterOS. See https://www.arednmesh.org/content/mikrotik-routeros-downgrade-issues .  

If anyone has a story on how to do this, I’d like to hear it.  Thanks.
-Tim K5RA