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A few question about KDE

Hello, I am a user of Cinnamon DE and I am determined to switch to KDE.
I have some questions about KDE that I'd be grateful if someone answer
to them.

1. Why the archive of "KDE" mailing list is private?
2. How much KDE is secure?
3. Why some Linux/UNIX guys hates C++?
4. At what level is the code quality of KDE?
5. Is C a bad language for developing big applications?
6. From what area are the most sponsors and donators to KDE?

Thanks and excuse me for bad English.