My KDEvelop uses the default Qt headers instead of KDE headers. How can I enable the option to choose KDE headers?
I use Debian. Also, what development packages are needed to write KDE (not generic Qt) apps?

What do you mean by that? The KDE headers have different names, e.g. KAction instead of QAction. I'm sure KDevelop doesn't include QAction when you write #include <KAction>?

As for what development packages you need, depends on your distribution and what applications you want to write. But usually cmake should tell you.

Greetings!