Hello Theodore, I would like to give you better information, but I have to be brief because I have a stupid cold at the moment and cannot concentrate.
1. Yes, the age should be blocked, I agree with you. But I had asked Diafero to unlock the Age for me to start with so that I can test it faster. But even so I didn't have time to do it because as soon as the book was on the shelf it was difficult to test the Age alone. Unfortunately, there is no better solution for this, because Diafero can't make the Age invisible.
2. Yes, the doors will close again when you leave the Age.
This is due to the script, because unfortunately I didn't have a better one. But it is actually not a problem because you can reach all places without a door and if not you are right in front of a door that can be opened with a switch right next to it. It is the same with the crystals. But as already mentioned, each player should be able to find the crystal himself and write down the corresponding number. If the crystal stone is open, you don't know the number; if it is closed, you don't know the crystal.
Therefore, it only helps to note everything down and finally solve everything at once
3. Clear the puzzle in the "Myst Generator" is one of the bugs I'm fixing right now. You can open all windows and close all doors there.
Usually you should have all the information you need by then.
The puzzle itself works, but there is a bug with the visible panels because i forgot to export.
It is not the beetles that are important, but what you see in the third window. When you have solved this puzzle, cloth 6 and 7 are child's play.
4. Yes, I also think that this age is more for 2-maximum 3 players who start together and do not hinder each other.
I also recommend the graphics settings to low and ant aliasing off, which I also wrote in the book as age information. (in the update for Diafero).
The Age will be released for offline play on UAM as soon as I have fixed the errors found (which may take some time because of my cold).
5. The door with the buttons can of course be opened with the clues, but if the decisive clue is missing, it will be difficult.
In addition, you need all the cloths first, otherwise you cannot do anything with these instructions.
6. Behind the said door it is unfortunately over for the time being because AlabastersDepths2 is not finished yet
Now I've written more than I wanted
I hope this helps to get started.