I'm sorry that I don't have any help to offer about your download/erase/program issues in uboot, other than to say that if you want to retry it, you have to catch it in that "auto out in four seconds" phase and enter "ard" - but you probably already know that since you say it keeps doing this.
Then, the Yun starts rebooting repeatedly probably due to the wifi-live-or-reset script.
That's possible, given that you say it reboots about a minute after the last messages.
Unfortunately, I don't think the rootFS is in a "good" state so I can't SSH to it or connect to the web UI.
If it's booting as far as it is, and the wifi-live-or-reset script is running, then you should be able to get to the command prompt, at least for the minute until it reboots. But you probably won't get there using a WiFi connection - if wifi-live-or-reset is resetting the board, then it's dong so because there is no WiFi connection.
Try making an Ethernet connection, or use the YunSerialTerminal connection (which you are using to get the boot messages.) The first thing I would try to do is disable wifi-live-or-reset by renaming it to something else:
cd /usr/bin
mv wifi-live-or-reset wifi-live-or-reset.disabled
This will rename the file so that it is not found the next time that the system boots. It will already have been launched, so just renaming won't disable it for this boot cycle, so the system will still reboot after a minute. But the next time that it boots up, the file shouldn't be found, and the endless reboot cycle should be over (if this is what is actually causing the reboots.)
I've tried holding down the wifi button for 5 seconds and then 35 seconds, but since I believe that I'm missing LuCi GUI I don't think this will help.
The LuCI GUI has nothing to do with it. This is a script that is started at the end of the boot process that monitors the WLAN RST button: when it is pressed, it saves the time, and when it is released it looks to see how long it's been pressed and calls an appropriate command.
When did you try pressing this button? It's not well documented, but this only works once the Linux system has fully booted. Lots of systems out there do a factory reset by pressing and holding a button immediately after power up, or even holding the button while applying power. The Yun doesn't work that way. You need to wait until it's fully booted before pressing it, but you have the problem that it resets quickly. So you need to press it once it's booted, and release it before the system reboots itself. This isn't going to be easy.
If you can get to the command prompt (using serial or Ethernet) before it resets, you can skip the button presses and just issue the commands that the button press would've triggered:
- long press: reset-to-factory-anyway && reboot
- short press: wifi-reset-and-reboot
Note that the last command, which is executed from a short button press, is the same command that is executed by wifi-live-or-reset if there is no WiFi connection. So, if wifi-live-or-reset is causing your reboot loop, it's unlikely that wifi-reset-and-reboot will fix anything.
I also question whether reset-to-factory-anyway is going to get you anywhere. It's possible that the reason you're rebooting has nothing to do with wifi-live-or-reset, but is due to a mismatch between the kernal and system images. I say this because you've successfully updated the uboot and kernel images, but ran into trouble with the system image. The kernel and system images must be a matched set. The reset-to-ractory-anyway is only going to update your system image, and will not restore the uboot and kernel images. I fear it's not going to help you here.
You really need to get that matching system image loaded through uboot, but I'm sorry I don't have any advice there.