Does a Factory Reset Reset Firmware, or Only Clear User Settings?

The firmware on my R6400v2 WiFi router was updated from what was shipped when I purchased the router eight months ago.  It now has firmware v1.0.4.102_10.0.75, which is the most recent version.  But, now I get nag screens whenever I log in.  I wanted to go back to the factory shipped firmware to see if the nag screens will go away.  The manual says, "Pressing the Reset button restores the factory settings."  I held in the reset button for over ten seconds, and the router did go offline and then rebooted, at which point I entered the IP address and was taken to the Netgear welcome screen.  From there, I logged in, and saw that the firmware version, as shown in the upper right hand corner, was still v1.0.4.102_10.0.75.  The nag screens were still there, too.  I tried a factory reset again, but still no luck.

1) I'm wondering if the manual is incorrect in saying that this 'hardware' method does a factory reset, as all it did was clear my custom configuration.

2) Within the browser interface, there is a screen that says, "Revert to Factory Default Settings...ERASE."  I wonder if this button is any different than the ineffective hardware method.

Bottom line...I suspect that either method only clears modifications that were made by the user, and does not revert to any earlier firmware version.  The only way to go back to an earlier firmware version is to download and install.  But, that may not be advisable because the older version may not be compatible with the newer version, and could brick the router.