Optional task location hints?

It's difficult to say exactly,because the maze is so complicated and I made it so long ago that I barely remember.
The IT department is, I think, somewhere after the construction site, but before the arena.
What were the other two?
I think there was the slums, which is in the first section near the beginning. And I don't remember what the third one was, but if you remind me, it may trigger my memory and I will be able to tell you where it is. Because there is a lot of stuff in that maze, but I don't remember, on which ones I put the optional tasks.