(2) couplets: from overlooking to looking up, (2) necklaces: from near to far;
(3) The first couplet uses imagination to imagine the gentle autumn wind heard all night as the autumn wind blowing among the drooping green vines, playing a pleasant sound.
Or: Tail couplet quotes allusions, imagining a leaf, moved by the dazzling waves, unable to help but despair, showing the poetry of a leaf following the waves in Dongting.