If you don’t have an account, regardless of the version you previously had, then you may require it with avast 9.

I still don’t know if you only have one avast installation (device) then there isn’t much point in having an account or if it is mandatory (wouldn’t make sense if it was an off-line system). You can monitor that single installation within your system.

Sorry “Also, what is the purpose of “device” in Avast9” isn’t very clear
If you mean the avastUI > My Devices, why don’t you try clicking on it - You still need to login then it opens in the avastUI not the browser my.avast.com portal.