I think he's referring to 1st floor as apposed to ground floor (as I can't find any windows you can pass through on the ground floor). If I'm right then he must be talking about the windows that are open and have no glass and I can go through them crouching no problem...
And I don't if you left this in on purpose or you didn't notice, but:
You can jump on the ceiling lights in the room between objectives B and C. I generally don't see real people jumping on lamps, so I thought that could be considered a restricted area...
Nice find with the lamps. I put playerblocks up there so people could do that if they figured it out

I fully intended for people to be able to do that.
I still don't know what outside path you're referring to. Could you post a screenshot?