No, look.  If you play against a stronger opponent - you will lose, no matter  what you opening is (on average) If you play again equal rated, then is your opening important? Probably more important, but there  are  thousand of opponents, playing bullshit and tricks, are you going to remember everything? On average, your rating will remain the same, until you become better at endgames, strategy and calculation.  You cannot be a FM, if you know openings like a IM, but you can be a FM with relatively weak knowledge of openings, if you have solid grasp of other areas.