Welcome @johncage to OM Forum.
Excellent questions. One suspects you must know a bit about Discover already.
Answers apply to our stable release only. Stable release is defined as using repositories called either Rock or Release.
The short answer is yes. But, there is always a but, OpenMandriva recommends users to upgrade from Konsole with:
$ sudo dnf clean all ; sudo dnf upgrade
Over time it is fair to say that OM has trouble keeping Discover working. The nature of our stable releases (currently Lx 4.2) is that we do not change things in the system packages and the tool chain so this is very unlikely to be a problem in our stable releases. This also results in our stable releases do not get a lot of package upgrades.
New OM Lx users may find this article helpful.
Short answer is emphatically no. There is a different command to correctly do a distro upgrade (or sync) and neither Discover of dnfDragora do this. Trying to do this with either is unlikely to work and if somehow does work the resulting system is very likely to have issues. The command to do the distribution upgrade is:
$ sudo dnf clean all ; sudo dnf distro-sync
Sometimes there are packaging problems and we need to add the option --allowerasing like this:
$ sudo dnf clean all ; sudo dnf --allowerasing distro-sync
For upgrading OM Lx 4.1 to 4.2 the process is described in detail here. We usually do a short article for each release.
Note: For new OM Lx users doing your package management from command line is a great way to get more comfortable using the command line. If you have questions about dnf or need to find a specific command or option remember:
$ dnf --help
$ man dnf