How To Properly Study Opening Using Book..??

Hi guys, today i just got a book called FCO (Fundamental Chess Openings), i just want to ask how to study an openin properly, what should i learn, and im confused what to do if our oppenets play another move that are not in the mainline or other variations, and im confused what the ideas of oppenings are like italia game what should i do next, or after finishing the opening set up what should i do next, Thanks

First of all, if you ever don't know what to do in the opening (like they play a move you haven't studied), then your default should be to just fall back on chess opening principles, since they are foundational to the opening stage of the game:

https://www.chess.com/blog/KeSetoKaiba/opening-principles-again

I also created a video 6 months ago, on the topic of punishing bad openings. It is mostly examples and the thought process for how to navigate the position.

As for the study of the openings you do encounter, your "study" will depend on what you want to get out of that opening and how likely you are to play it regularly or not. For most openings, you'll just want to learn the key patterns and ideas for both sides more than memorizing specific moves and variations.

you have actually asked three different questions. the first, how do I study an opening properly? that has already been answered. you must learn the ideas of what you and your opponent are trying to accomplish by the specific placement of the pieces. two, what do I do if my opponent deviates from a specific move order? you must think for yourself. one idea is if your opponent makes a different move than what is the expected move, make the very next move that you are supposed to make in the sequence UNLESS there is a reason that you should not. three, what do I do once I have completed set up? congratulations you have made it to the middle game and now you need to make a plan and concentrate on tactics both for and against you.

My method of studying an opening isn't very popular.

Check my rating, though, before you decide that I don't know what I'm talking about.

It goes like this :

1. Play a game using that opening.
2. Lose horribly.
3. Figure out exactly WHY I lost that game.
4. Play the opening again, avoiding that particular error.
5. Lose horribly again, but in a completely different way.
6. Go to 3.

This might strike you as a rather stupid way to learn an opening... but in fact it works pretty well. You REMEMBER your losses. Especially if you got badly rekt.

Also... find some master games in that specific line, and play through the WHOLE game, from move 1 to Resigns. That way you learn not just a sequence of isolated moves, but also key squares, typical plans, typical tactics, and the types of end-games associated with that opening.

This actually seems to be very reasonable

I think a lot of young players have an ego that is too fragile to withstand repeated disastrous losses, without abandoning their intention of learning that line.

Sir Winston Churchill used to point out that one necessary ingredient to eventual success was the ability to go from failure to failure without loss of enthusiasm.

blueemu has said another truth about learning an opening. you can study an opening till the cows come home but there is no guarantee that you will remember and play through that academic knowledge in practical experience. example: you can read everything book on whittling ever written but it will not keep you from cutting your finger but you will always have a little scar to remind you why you were not supposed to do that.

How I learn an opening is I learn the first few moves of the popular variations of the opening and then play from there and analyse them .

The difference between Theory and Practice is that, in theory, there IS no difference between Theory and Practice, while in practice, there always IS.