I'm so sorry about my mistake with your name. Please overlook it.
Thank you so much for your kind offer of further help. Actually, there was one thing:
I quote the opera “Руслан и Людмила”:
Дай, Перун, булатный меч мне по руке,
Богатырский, закалённый в битвах меч,
В роковую бурю громом ско́ванный
Now, I've always thought that one should use в + locative (also known as the prepositional) for location in a place (в ко́мнате = in the room) and в + accusative for location in time (в час = at one o’clock). So why is it В рокову́ю бу́рю here and not В роково́й бу́ре?
Best wishes, and many thanks again,
It is в because it is actually location in time, роковая буря - deadly storm, is not a place, but moment in time when the action takes place. The sword was forged by Thunder during a deadly storm. If we transform the poem we can see how prepositions can be changed too, so that the time aspect becomes obvious.
Перун, дай мне подходящий богатырский меч, скованный громом во время роковой бури и закаленный в битвах.
PS if you use Skype, you can text me, it is more likely I will give you a timely response.