I've never heard that the form "Avgusteishee" was used in a style.
Princes [non-imperial, knyaz'] and counts [graf] were addressed using the same style "Vashe Siyatel'stvo". Serene princes [svetleyshiy knyaz']: "Vasha Svetlost'".
Thank you. Indeed the "vashe siytalstvo" is correct and the "vasha svetlost" is correct. Thank you.
As for "agusteeshee", it was used.
And no, not all the announcements were in French, Mike. For example, upon reception at the Duma, the announcements were in Russian. Had They been announced in French at the Duma, that would have caused a "furore". And in State Proclamations they were surely not announced in French.
As for the Papal Nuncio, I was not aware that Imperial Russia maintained separate relations with the Vatican prior to revolution, considering that the Vatican itself was only formalized in 1929 with the Lanterne Treaty. Prior to that there were the Papal States and a United Italy.
But that is easy enough to determine. And it is a good question.
One other point for our readers, however, Nicolas II was definitely :
"We, Nicholas II, etc., etc."
"Mbi, Nikolai, II," and in formal documents "padumaem i reshaem" which came came after his long list of titles (which ended with i prochee i tak dalia")
Thank you for your help.