I am using Ubuntu 16.04 LTS and I would like to downgrade Unity to version 7.3.2 (Ubuntu 15) or to version 7.2.6 (Ubuntu 14). I know that there are some dependency issues, but is it possible to fix these dependency issues? So, just in case that this is possible ... how can I downgrade Unity?
SnapOverflow
Possible is more or less everything - but is it recommended to even give it a try in this very special case ? No, not - absolutely not ! You most probably will break the whole operating system and not only because of missing dependencies. Every Unity version is deeply integrated into the matching Ubuntu operating system and the repositories are tied to the edition which is installed and in use.
Just as an example : Unity 7.2 is a part of Ubuntu 14.04 (Ubuntu 15.10 is not supported anymore), these packages are not included in the Ubuntu 16.04 repositories ... which means that everything would have to be done manually. What could be possible though is downgrading packages within the Ubuntu Unity version 7.4 : Unity packages from xenial-updates to Unity packages from xenial
You are using Ubuntu 16.04 LTS and it is highly recommended to stick with the originally included Ubuntu Unity desktop version which comes pre-installed. But just in case you want to downgrade Unity nevertheless, here's a list of dependent packages which would have to be downgraded, it's up to you to decide if it's worth the effort - especially when you probably could end up in a mess.