The fate of the french monarchy was sealed by the king's flight to varennesdo you agree?

Yes. He was probably doomed anyway, but the flight put the liud on it. It was an obvious, irrefutable attempt to join the army that was at war with France, at a time when the declaration of 'La Patrie en Danger' was in force. Before Varennes, Louis XVI could have given in and genuinely accepted a constitution. It would have been utterly out of character and probably a personal impossibility, but the choice existed. After Varennes, he was guilty of treason and. as I said, doomed.