Is the Update Manager (or Software Updater) the frontend of apt-get dist-upgrade?
Software Centre and the apt suite (
apt-cache) are all front-ends to
dpkg so anything that can be done with one can done with the others, but it is usually much easier to use the GUI tools which will also handle editing the config files automaically.
Note that the only
dpkg command that most people use directly is
dpkg --configure -a to fix things up when an install fails.
In a way yes. However the Update Manager combines a lot of
apt-get commands that may depend on your update settings.
You can have a better understanding of
apt-get options if you read the AptGet/Howto.Then you can figure out which GUI option correspond to which
Update-manager is essentially a GUI frontend for
apt, which includes
dist-upgrade functionality. Using the Update Manager is more convenient than using
apt-get dist-upgrade, because using this command to upgrade to a new version of your distribution requires the modification of configuration files. There is less room for error using the Update Manager than using
do-release-upgrade is a command line tool similar to the Update Manager, which also does not require modification of apt configuration files.