Hi,
So i stupidly updated all of the software on my router using a script and now my qos, adblock and upnp aren't working. I suspect other things are probably broken too.
I just wanted to make sure that "reset to defaults" under System - Backup/Flash Firmware will remove all software and settings?
Yes. Resetting to defaults will erase any user installed packages and also al of the configuration files. You can make a backup if you want to preserve the config files.
Regarding the upgrading of packages…
Upgrading packages (via the CLI opkg upgrade command or the LuCI Upgrade... button) can result in major problems. It is generally highly discouraged, unless you know what you are doing or if there is specific instruction to do so.