Yes, but false negatives fall through. I don't pay for the call screening; maybe a paid version would be more successful.

Mostly ignore unknown numbers, but if I'm expecting a call, I will pick up.

My colleagues regularly get calls from nurseries, daycare, parents at the after school club, friends of their children or their parents and so on.

They can probably ignore international calls, although only probably.

Yep, if the number is not in my comtacts, it goes straight to voicemail.