unity - Questions about reinstallation

I reinstalled Ubuntu and got a system without internet.
After deleting all types of drivers and putting important drivers and resetting network, it worked.
Recently, I installed pantheon and mate, and they thrashed Unity.
I removed all of them, and reinstalled Unity, it didn't work.
I Installed the ubuntu-gnome-desktop meta package and installed GNOME 3.12 from the staging ppa.
Attempted a downgrade to 3.10 and it never worked. A destroyed apt and Ubuntu install, which was converted to Ubuntu GNOME, missing Unity and a stable system, I decided to fix this up.
I used to run Ubuntu 14.04.1, now Ubuntu GNOME 14.04.1. I have an Ubuntu 14.04.1 live cd.

So here are my questions.

1-I know about a reinstall while keeping data option in Ubiquity, but is there an option to switch over remixes, for example Kubuntu to Xubuntu and vice versa?

2-If there is such an option, will it replace GNOME with Unity wherever possible, just keep my data? I do not care much about programs, I will backup /usr/share/applications/whatever icons i created and /opt and use Aptik for the rest, but it would be more convenient for me.

3-If there is not such an option, what all do I backup, other than the ones mentioned above?

4-Which one method is more recommended, in-place or fresh with backup and restore install?

Please help me, as my system is strangely unstable.

1. It is and it isn't. Some data will be lost, so it is sensible to do a full backup anyway.




2. If you install Kubuntu / Xubuntu you won't have unity. You will have Plasma / XFCE. It will remove the current DE though, yes.




3. I would suggest you backup /home/USER and also run the command dpkg --get-selections | grep -v deinstall. That will give you a list of the programs currently installed. Don't just copy them immediately. That could break it because of hidden files.




4. I would advise new install, it is less likely to have recurring problems (like mutations in DNA get worse over time, so do bugs sometimes). However, installing all from the list isn't always the best idea, it can cause dependency left over if you uninstall.