I don't know anything about the "David" firmware versions, but unless there are specific features that you need in that firmware, you might want to simply flash with the normal 17.01.4 release build for your device.
That said, you should be able to reset any OpenWRT/LEDE release to defaults by ssh'ing into your device and running: firstboot
and then rebooting.
Alternatively, using the LuCI web UI, you can go to System > Backup / Flash Firmware > Reset to defaults.
@psherman : Davidc502 LEDE build is a little bit more up to date. The wireguard package are more recent. I looking for a stable and update version of LEDE (specially for wireguard.).
@mk24 : So .bin image reset everything ? Like stock to LEDE for exemple ?
@anomeome : Thanks ! This command just reset the setting or reset completly the OS ? Like clean install from stock to LEDE ?