Novice Opening Question

tl;dr version in bold
There are some opening setups that can be played mostly (but not completely) without paying attention to the opponent's moves.
There are also setups which can be played against a class of openings. As long as the opponent enters the opening, then you can apply that system of play, and again mostly ignoring their moves.
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Most named openings though are a series of moves by both players. For example the Ruy Lopez isn't a white or a black opening, it's an opening both players agree to enter after 1.e4 e5 2.Nf3 Nc6 3.Bb5
From here there are many variations of the Ruy, and with each move the players will narrow it down more and more. Either player can also leave known lines at any point they wish. In either case, unlike the system type openings, the players are prepared to play many different moves depending on what their opponent does.
Some openings are very tactical, and it's certain disaster to not play the recommended move(s). In other openings there are many options, to the point where in some positions nearly every legal move is reasonable.
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Openings can also transpose into other openings. You may start off with a Sicilian, and end up in a Ruy for example. Or start with a Nimzo Indian and enter a Queen's Gambit.
And finally, there are well known positions which can be reached from many different openings. Perhaps the best example here is the classic position where white has an isolated queen's pawn.

Don't fret too much about named openings for the time being. Learn the principles: get your pieces to better squares, get your king to safety, fight for a share of the centre where pieces have the most mobility, avoid losing material, win material if it is at all safe to do so. Usually it is unless you can see an obvious problem -- even if the opponent is making a deliberate sacrifice, you should strongly consider accepting it and making them prove that it works.
Answer: A good thinking system favors a good opening repetoire.... You can't just follow the opening theory. Imagine if you are taken out of theory example like you expect white to play e4 (you preapared against it) and instead of e4 white starts with b3! (Nimzo-Larsen Attack). What to do now? You are on your own. Don't relay on too much opening theory. Many beginners even ametaurs make this mistake. You need to learn how to play the opening, not just cram openings theory. Instead work on your Strategic and Tactical Thinking system as well as endgames. Good luck with chess progress and have a nice day!