Knoppix has KDevelop which seems like a fairly complete IDE to me. It has libraries for C/C++, Qt and KDE. However I could not find the documentation for these libraries and there was no graphical screendesigner. But I didn't have a very thorough look.

To your second question: if the object is to learn concepts, nothing beats SmallTalk for learning OO-concepts, IMHO of course. It is not included with Knoppix, I am not sure if it may be distributed freely, but it's non-commercial use is free. I'm talking about VisualWorks SmallTalk here, I heard there was a GNU SmallTalk as well, but I am not sure.

As an alternative: Python. Open source and included in Knoppix.

- - Edwin