I think only once it is installed. If you do it on the intial installation, it wont install. But I could be wrong.
yeah i think you can just do a custom install and just choose to install the on demand scanner only. I know you can do this in the premium version, i'm not 100% sure about the free version.
You can. The install is pretty modular, and I have installed it as on-demand before with only the free version Cheers, Alphalutra1
If you already installed Avira completely, you can disable the Guard In the Control Panel->Administrative Tools->Services Open Services and find "Avira Antivir Guard" or something related to Guard. Double click it and set "Automatic" to "manual". With this, the Guard Service will not load on startup.
It still will have the drivers installed though, and conflicts can occur with other real-time avs. instead, if you already have it installed, you can redownload the antivir install package, then run it, select the modify option, then select to remove the guard. Cheers, Alphalutra1