Re. 2. That isn't the question I asked, in ZA's Programs section is avast.setup allowed access to the internet?
Removing the Compatibility line entry from the avast4.ini file (you can't edit avast.setup) for ZA Compatibility relates only to web shield, won't effect whether ZA allows avast.setup or not, that can only be achieved in ZA.
Re. 3. I still don't understand, please explain what it is you are trying to do.
ZA and avast do work well together the only compatibility issue relates to the Privacy controls that are only available in ZA Pro. There really are only three files that need internet access, ashMaiSv.exe (avast Mail Server), ashWebSV.exe (avast Web Shield) and avast.setup, which handles the avast updates.
Try this and tell me what happens.
Right click the avast icon, Updating, and select iAVS Update. avast will now try check for updates (you need to be connected to the internet already), ZA may ask if avast.setup should be allowed access, say yes. If ZA doesn't ask permission it may already be blocked