Now, I don't pretend to know more about Japanese than what I've gleaned from years of (paying rather close attention to) anime, but I wonder if you can help me with this, @Nikolaos :
I'v heard небёс before. Could have been a dialect of some sort.Just when you think you've got Russian pegged, it comes undone. I would have assumed the gen. plural of небо would rather be *небёс. In fact, so it should be, & the Polish lyric corroborates. Увы!