I looked around for a few hours to find these and as far I know there are 29 30, but I've probably missed some?
Here's an album with a screenshot of each with the answer written below in description: https://imgur.com/a/wak3U4X
If you answer wrong: 'the Wall' laughs.
If you answer right: 'the Wall' starts to speak Requiem sentences, which is a whole another can of worms to decipher.
These texts are suprisingly blunt about Lore details, which I find quite fascinating.
I just had a rather horrifying realisation.
When Albrecht Entrati went into the void, he was confronted by a being that wore his own face, and after returning, he was forever haunted by the idea that it wasn't him who made it back.
Could it be the case that, rather than time-split counterparts of one another, the Operator was the Drifter's void doppelganger? The fact that they seem to be much more susceptible to possession by the Man in the Wall has some troubling implications.