applications like Kcalc, Amarok, almost everything listed here: https://www.kde.org/applications/ is not installed for some reason.
I upgraded from Minimal X Window to KDE Plasma 5.
How can I get the applications? Do I need to install some package?
EDIT: I could install one-by-one, isn’t there a way to install them all at once??
Well, those Applications are not installed when doing a “Minimum X Windows” install for obvious reasons (that’s why it’s called “Minimum”).
And they are not part of Plasma5 either. Some of them (Amarok e.g.) are not even ported to KDE Frameworks5 yet.
So they are not installed when you install Plasma5.
How can I get the applications? Do I need to install some package?
EDIT: I could install one-by-one, isn’t there a way to install them all at once??
You could install the “KDE4 Desktop Environment” pattern in YaST->Software Management (View->Patterns), and maybe some other patterns.
Or do a fresh KDE install (a normal one, not “Minimum”) and switch to Plasma5 afterwards, and you’ll have them too.
I don’t even have ALSA installed, so audio isn’t working 
I followed this guide: Installing KDE5 on OpenSUSE 13.2 as the only desktop enviorment | PoisonPacket
So should I reinstall and choose KDE instead and then upgrade from KDE4 to Plasma5?
Hm, TBH I very much doubt that (much of ALSA is part of the kernel anyway), but I never tried a minimal X Windows install myself.
I followed this guide: Installing KDE5 on OpenSUSE 13.2 as the only desktop enviorment | PoisonPacket
Well, that article seems to be focussed on not getting unnecessary packages installed.
But if you start from a minimal install, you don’t have any KDE applications installed. That’s the point of a minimal install.
You have to install manually what you want, even if that article doesn’t explicitly mention it.
Btw, the article is wrong in at least one aspect: sddm works fine in 13.2. It’s gnome-keyring-pam that causes the hang on logout (has been fixed in later versions, but those are not included in 13.2), uninstall that if you want to use sddm if it is installed.
To switch to sddm, just set DISPLAYMANAGER=“sddm” in /etc/sysconfig/displaymanager after you installed sddm.
But you can of course just continue to use kdm (or any other dm) too.
So should I reinstall and choose KDE instead and then upgrade from KDE4 to Plasma5?
I would recommend that, yes.
Just install the package “plasma5-session” afterwards, and accept the removal of the KDE4 desktop.
PS: openSUSE 13.2 doesn’t contain any KF5 based applications other than those that are part of Plasma5 itself.
You probably should add the KDE:Applications repo as well, and do a full switch to it to get the latest KDE applications.