A program update ultimately requires a restart in order to change any low level files in use.
As far as not knowing if you have the avast cleanup installed, check the AvastUI > Settings > Components - that will tell you what components you have installed.
I don't know what you mean by "one of the start up programs did have a update ready." This could be from its own update function (depending on the program, which you don't mention). Or do you mean the avast Software Updater, which monitors programs that are more prone to exploit if not kept up to date. This doesn't necessarily update all startup programs.