How to reset application rules in firewall?
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Try this
Avast.com / support button in top right corner / FAQ
Tried it already, couldn’t find anything.
This might help https://support3.avast.com/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=1395 
I did see that, nowhere says how to delete every rule in there. I am not going to delete every application and then application group one by one.