Does chess openings really matter if you will win or not?

Openings definetly matter, but not learning theory. (It matters but not very much until you are more advanced). In this game, He pretty much lost in the opening. He blundered his knight and I maintained pressure on him the whole game. 
https://www.chess.com/a/rf87ummpjuE6

So you mean opening principles matter. Not exactly the opening itself. I mean, most players would have known the basic of opening pitfalls like scholar's mate after days of playing.

Of course, I have lost to scholar's mate many times when I was new to chess. But now I learnt to counter it.

indeed. Another opening type theme question (same context, diff semantics) importance or not? Weird. I never get the problem of a player's understanding or misunderstanding the importance of establishing an opening repertoire. 🤔

At ANY level. Basic Opening Principles are just a guide when one has No prior knowledge, definitely not a end all to conduct an opening thoroughly through to the middle game

BOP (Basic Opening Principles) does not account for using initiative, pawn structure, force, inherent tactics, dark square, light square strategies, endgame ramifications.

indeed. Establishing an Opening Repertoire for yourself, early on is a win win. Even if you dont fully know the theory, at least you know what you will play whether white or black. I had a friend who only played (1. c4, 1. ... c5) one way-no matter what. ( In this case, he only played the English, the Sicilian, the Benoni) but he really didn't know much theory... but as it is, he had experience which kind of made up for it because he ONLY played one way~his opening repertoire was just based on c4/c5.

(plus, of course, he had some talent & innate skill ar the game)

indeed. As a grass roots player (30 yrs of playing but no prestigious title to speak of) sure, it's cool to read on "how this..." or "how that..." but in a practical sense~isn't the saying, "the More you Know" like, Practical? If you're just playing a casual game, no qualms about winning or losing I can see one not caring a lick, about BOP, Theory etc. Soo what does it matter? I guess it's what some would say the OP is trying to convey. But if the OP is trying to say that if one wins despite BOP, Opening Theory but rather on blunders, oversight, winning vs complete noobs then it's cool too. But hell I'd be damned if I'm going to recommend that.😎

All those folks talking about not doing deep dives into openings? I used to not like that advice until I actually played in some OTB tourneys. It turns out they're right. (That's not to say don't look at videos, just don't spend your time memorizing stuff -- unless you have comparatively unlimited chess study time. Otherwise, spend time more efficiently).

Here's a simple test. Look at your last 10 losses. With the aid of an engine, ask yourself the following question: did you miss a tactic that you could have played that would have won you at least a pawn, or did you allow such a tactic? Dan Heisman asserts that when there are two players who are under 1600, the odds are 99% that at least one of them missed at least one tactic.

If that's the case, then the most efficient road to improvement, he asserts, is "removing the negatives" (i.e., missing tactics) rather than "adding positives" (learning strategies and openings).
That doesn't mean you should spend 100% of the time studying tactics. But it is to say that you get your most bang for your buck by putting the following four items at the top of your priority list: tactics, playing, analyzing one's own games, and reading annotated game collections.

Again, that's not to say don't learn anything else! But, as everybody keeps saying, don't invest too much time into openings if you're going to miss a tactic later on anyway.

When new players learn openings they need to learn the tactics and positional ideas associated with it... then it is important. Memorizing does no one good, especially not at lower levels because they will have no clue what the moves do.

Yes, excellent advice! I'm already taking part in three thematic tournaments.

I think your brain saves opening patterns analogue to checkmate patterns. For example, I've learned Scholar's mate from a book looong before we had access to the internet.  On a physical board. I never fell into this trap, it's so easy to avoid. And I never tried to lure someone into this trap, because Df6 is a bad development move.

But I've learned about the vulnerably of F7 by those considerations, which helped me a lot in other games. 

Therefore I'm a little reluctant to agree with this 99% tactics meme. Of course I agree it's a waste of time to learn opening lines to the 36. move by heart. But studying some to the first 4-5 moves as examples is really helpful, I suppose.  

Yes, learning lines is learning nothing. But to understand the positional and strategical ideas behind the openings is the point. 

I don't agree with 99% tactics either, but I do think they are incredibly important.

As I noted in an earlier post, do this experiment: look at your last 10 losses and try to figure out the biggest reason you lost, and/or the most significant move that took you to a position where you fell significantly behind in evaluation. 

What proportion of those moves were (a) you missed a tactic (either by yourself or allowed it by your opponent); or (b) positional/pawn structure/other reasons?

Dan Heisman asserts that if both players are under 1600, then by far the most common reason is (a) -- missed tactics.

I play at the expert/master level, and even at that level, the most common reason for losing is: missed tactics.

I'd argue that this is true even at the grandmaster level ...

I will always tell people openings are important. For new players they should learn where their pieces belong and there's tons of tactics in the opening that new players fall for. I don't think people should look at it as just theory or memorization. Openings is a huge part that sets up the rest of the game.

Even people who argue otherwise and show examples... show themselves playing an opening well based off experience and knowing where pieces belong. New players don't do this. Memorization also won't fix it since positions change too much in lower rated games.

When I was 13 I got a copy of Modern Chess Openings and would set up and play through the positions on the board for hours and try to understand after each move why it was good. I didn't just do this for the openings I played, but also for openings that I didn't play.

I don't think anything I ever did helped me improve as much as doing this. Was I just memorizing moves because I was studying openings? No. I was learning what good squares were. I was learning to look for non-obvious moves. I was learning to look past a single move and rerouting pieces to better squares. At least once a day I would have an "aha!" moment. When you *really* study openings, not just memorizing moves, you learn a lot about how chess works.

Just applying principles doesn't do this. Principles are basic ideas without guidance. Doing puzzles doesn't do this. Puzzle positions are tactical and don't provide ideas on how to set up the puzzle position.

theory isn't really necessary however knowing an opening is useful and spending maybe 30-60 minutes learning your openings can bring you a long way. the point of theory and opening is to gain an advantage, in low-level games these advantages can be reduced to nothing in one move. and i would consider my games in that category too