I don’t like the new UI but want to use Avast. Is there any way to download official 2016 version of avast? 
Does Avast keep old versions ?NO
OK I hope in the future this will be changed 
If anyone is searching for older FREE version http://files.avast.com/iavs5x/avast_free_antivirus_setup.exe
Premier http://files.avast.com/iavs5x/avast_premier_antivirus_setup.exe
Is there any AV vendors that does that?
There is a good reason why it is best to use latest version, malware constantly change and so does the the technology needed to detect.
It has been this way for as long as I can remember (just over 13 years) of using avast free, so I can’t see it changing anytime soon.
Since development effectively stops on old version versions any bugs, etc. would remain.
If you go to places like FileHippo or FileHorse you may find old versions but unless they’re AVAST offline installers it’ll still automatically update you to the latest version during the installation process.
There have been threads about this for as long as I can remember so I doubt AVAST are ever going to make older versions available themselves.
This is a fairly recent discussion and some useful links on the subject:-
A more precise answer to the question is yes.
avast does keep a copy of old versions, but they don’t make them available for download (at least not to the public).
If you want a old(er) version, you will need to search for it.
If I have software I like, I always store a copy (full installer of course) on a storage medium.
I know for sure know that I even have a copy of version 4.x laying around here somewhere 
^ Yep, I’ve been doing that too for years and its helped to roll back other software a number times. most typically when it had been ‘updated’ and then found to cause problems. Only once with AVAST though and that was actually using an old installer version that came on what was then a two year old (UK) PC magazine cover disc. Still have that somewhere.
Its always worth keeping copies of old installers for programs you rely on IMHO.
You should always keep the installers, even if the newest version is working fine. Unless you are short on disk space, but then you can always put them on a Flash Drive or on a CD … You can find the other versions of Avast on this site:
“[b]http://www.filesetups.com/[/b]”