Justine? Text Behind Stairs? Letter In Glass Case?

[Ratsneve]

Tried searching but found little to none to these questions... I have the Steam version in English.

1. Where does Justine fit into the story--a sequel? How long and tough is it? Similar to ATDD?

2. I've just started the game following the pink liquid and found something not mentioned in either walkthrough. I don't know if it relates to the actual game or to something Steam is doing? Sooo...you go up the first set of stone stairs, around some corners, down an open hallway with one or two more rooms off it (?) and then down another similar set of stone stairs. At the bottom you can immediately turn 180 degrees and walk back on either side of this stone staircase to a sort of hidden area behind the stairs. On the wall here there is some easily read writing with some numbers or math to the right of each line--none of which makes any sense. ??

3. In the hall back up above the stairs mentioned in 2 above there is a table/case with a note/letter covered by glass. You can break the glass but cannot get the note/read the note/letter? Is there something I'm missing doing here? With either 2 or 3??

Thank you. Do you think questions of this sort about the game are better suited here or in the Steam forum or it doesn't matter?