Hello!

How does exactly do they work?

I was playing with Linda and I have John on 14 skill points level, when I died Father's Protection didn't cast, why is that?

If I were to guess, that's because those buffs only become active with multiple players.

They have worked for me in single player atleast the ones I have unlocked that are obvious ones ...So maybe some are multiplayer specific and others are for single player aswell

All works in single player. Either you didn't notice (not hard in hot situation) or used it earlier and was within cooldown.