Must I have an active internet connection during installation?

Hi all,

I wanted to update to the new CIS4 and ran into lots of problems. Installation wouldn’t go thorugh (3 times) but the old version was already gone. So I tried again and in the end it installed.

But I had the internet conneciton turned off the whole time for security reasons and i just read that comodo downloads needed files. Is that true? Is the installation somehow incomplete?

P.S.: Is there a way to check if the installation is clean and all old files were removed properly?