1. Judging the fact that the cencors look the same in pics 1 and 3, I'd say those were early versions of what cencors looked like in Raz's brain, or maybe it was intended to be someone elses originally, I don't know.
2. Milla's, hands down. Remember all the TVs all over the place? I assume thos cameras would film Raz as he went through the level and put him on the TV screens as well.
3. Same as 1.
4. I assume this was part of the milkman conspiracy, and you were supposed to go through vents at some point in the book depository r the post office, and you would stumble into the vent pictured. Only a guess though.