1) It's misleading to say Rostov was under house arrest b/c of his association with a revolutionary poem, it implies the poem was the reason for his being in trouble. He was arrested b/c he was an aristocrat/of the nobility. He owes his life to his association with the poem in that he was sentenced to house arrest instead of being shot after his trial.
2) When the count first met Abram, the taste of honey he was given was not from the apples of Nizhny Novgorod. It tasted of lilacs (page 127). It was many visits later (page 166) that the honey tasted of apples.
3) Sofia was not 17 when she was chosen to go to Paris on the goodwill tour. Sofia is five in 1938 when Nina leaves her in Rostov's care. It is 1954 when she departs for Paris, and she is 21. (page 379)