1. I wouldn’t consider that an anomaly as it is possible that it may have been in use at the time, but possibly the avast self-defence may have an interaction.

  2. The new uninstall utility (the link given) is capable of uninstalling previous avast versions.

  3. Yes it is possible (though not an immediate risk) you don’t have to be browsing as the connection is made and some exploits can try connection to randomly selected IP addresses. But it isn’t something that you want to do if you can avoid it, e.g. have previously downloaded avast and firewall (security based applications) on another system with protection.

These applications can then be saved to USB or CD, etc. Now you can install those applications by transferring them to the new systems. That said many new programs come with some programs pre-installed, that may or may not include an anti-virus.