On page 1 in Amelias dairy she writes the name of her sisters: Lea and Flora. She does not mention the name of her brother till page 6: "My little brother Ri'Jane..." Later she explains that she like to call him Jean, his name in Ne'Terra.

I concluded that Flora loves story, because on page 4 in her diary Amelia mentions that she gets the subjects for her paintings from Flora, who has much imagination. Later she writes that Flora has a passion for reading. You can find a book in her room (which is next to Marie-Anne's room, as is mentioned in the dairy). The room is not a study, so her books are obviously more fiction books.

I could not find until now any clue on how to solve the marbles puzzle but it can be solved using, once more, the assumption that there's no repetitions - the first marble is green.

As Greyfuss mentioned the clues are right there on the face - look for the colored circles then align the 'number' of circles up with the black marks on the face. The mouth will open when correct.

cannot be lit. It is the room down the corridor blocked by the boulders. Now its time to activate the button under the light panel that has not been working in the Star Chart room, hmmm...what to do with the clue....

the black spots are the key positions for the combination

The easier way to do it is to set the levers to a starting position were the gauge shows 0, them turn the first valve 1 turn at a time until you press the switch and the gauge moves to 5. Repeat the process for the other 4 levers until the gauge hits 25 (since there's no repetitions, you can skip the lever positions that are already correct).

[/spoiler]I counted the number of coloured circles and applied that to the same coloured eyes[spoiler]

put the correct number of coloured circles in the nearest position to the correspondig dark spot.

Now its time to activate the button under the light panel that has not been working in the Star Chart room, hmmm...what to do with the clue....

If you have the Star Chart lit over the Star Map....The shinning stars will show you the way

You just need to know/understand the numbering system, look at the gravestone and do some math - it will not give you the exact age but a range of 10 numbers (with 3 digits each) to try on the stone keypad since the first and last number on the gravestone dates are not readable!

I read the "Memory #5" book, but other than the lever on the same table, that seems to do nothing, I am not finding any interactive areas. I see book case, but none of it lets me click it. I assume I am in D'ni, it is very much like the room Atrus was trapped in (but it is strange we are using some sort of Ghen style powered book tech).