Eddy
3
1] All av applications do not detect everything. Avast is no exception to the rule.
2] If something is detected or not also depends on your settings.
3] Every malware sample submitted to Alwil will be implemented in the vps. But they can not do so if the sample doesn’t contain the whole code. And they (ofcourse) give priority to the ones that form a large security risk.
4] There is always the option to use a online scanner as backup to Avast. No need to install a second av.