Turnaround: I "noticed" this years ago. I never took it as anything but a standard design element in the games. Also it makes sense that you wouldn't always have a straight line to the goal and/or it makes the stage a little longer.
Hand: Yeah, like the article guesses (but doesn't know), Inafune drew or designed pretty much all the illustrations up to Mega Man 8, when he got so busy that another guy took over.
Pipe: Weird and I didn't notice it, but why wouldn't a building have an exhaust pipe? Like, a ventilation pipe for air systems or whatever. It's not really as amazing as practical.
PL: "definitely"