I upgraded from Ubuntu 16.04 to Ubuntu 18.04, made some wrong selections while upgrading, Can I use Ubuntu installed on usb stick (dd The Native Linux Cloning Tool) to upgrade or downgrade Ubuntu ?
You can clone from the iso file to a USB stick and use that USB stick to boot Ubuntu live and install Ubuntu into the internal drive.
dd is a cloning tool, but it is risky because it does what you tell it to do without any question. If you tell it to wipe the family pictures it will do it. A minor typing error may create chaos. You must be very careful, check and double-check that everything is correct before you press the Enter key.
Instead I recommend a tool with a final checkpoint,
in Ubuntu 16.04 LTS and newer versions: Startup Disk Creator alias
in Ubuntu 14.04 LTS and newer versions: Disks alias
in Ubuntu 12.04 LTS and newer versions and other main linux distros: mkusb
in Windows: Win32 Disk Imager
in Windows: Rufus - an extracting tool and a cloning tool
in MacOS: Unetbootin - an extracting tool (not a cloning tool)