Sarushka, I don't have any precise dates about those letters, it is only said that they are from 1914 and later...
Here are some quotes. I first put them in French this way if any French speaker thinks I did a mistake in the translation, this person could tell me.
"
Que personne n'ose dire "tu m'appartiens"! Tu es à moi, tout à moi, pas à elle..." "That no one dares to say "you belong to me"! You're mine, all mine, not hers..."
"Si nous ne tenons pas bon tous les deux, nous aurons encore des scènes et des scandales, comme en Crimée.""If both of us don't hold fast, we'll get scenes and scandals again, as it happened in Crimea."
"Tu verras que dès notre retour elle te dira combien terriblement elle a souffert de ton absence...""You'll see that once we return she'll tell you how dreadfully she suffered from you absence."
"Chéri, tu brûles ses lettres pour qu'elles ne tombent jamais dans d'autres mains?" "Darling, you burn her letters for them not to be discovered by anyone else?"
[translated in a more accurate way to French it should be: "Darling, you burn her letters for them not to fall in any other hands?" But it quite means the same thing. ] Sorry, it is roughly translated... But it may remind you something, Sarushka?
As you can notice, Alix never directly meant Ania but Pierre Lorrain thinks that's her. So does Radzinsky (sp?) if I remember well.