@1
"practice tactics" ++ Yes, but neither overdo it nor rely on it.
"learn openings" ++ No, a waste of time and energy better spent on learning endgames.
"study master games" ++ Yes, but even better analyse your own lost games.
"what is the best way to apply the lessons in a real game?" ++ Play and analyse your losses.
"My puzzles rating is 2300+, which is obviously master strength"
++ No, it is not. Puzzle rating is exaggerated.
"puzzle rush or puzzle battle" ++ That is a matter of speed.
"Why is there this discrepancy" ++ In a real game nobody tells you there is a tactic, or for whom.
"what can I do to remedy it?" ++ Four tactics puzzles are a good warm-up, but no more.
"What is the importance of learning an opening" ++ None at all.
It only postpones the moment you have to think for yourself.
That what you learn does not happen and when it finally happens you will have forgotten.
"what benefits does it confer beyond those that a solid grasp of how to develop already do?" ++ None at all.
"what can I do to make sure that I am able to learn lessons from a master's sometimes obscure moves" ++ When you see an 'obscure' move, try to understand it.
Look at the consequences of other moves to understand the meaning of the 'obscure' move.
"apply these lessons in the arguably very dissimilar of a real game?" ++ You have to study thoroughly to assimilate the ideas and then you can apply similar ideas in different games.
Analysis of your own lost games is more important. It has happened and will happen again.
I am rated 1800+ at the moment and have a peak rating of 1900 that I keep inexplicably losing and regaining.
I am confident I could reach 2000+ if I applied more serious training, but when I search for "how to improve at chess" I get cut-and-paste results.
Merit must be in these practices if they're so commonly repeated, but what is that said merit and what is the best way to apply the lessons in a real game?
Let's take an example, say "practice tactics". People pay this a lot of lip service, and I have been doing so. My puzzles rating is 2300+, which is obviously master strength, yet the most I've ever been able to reach in puzzle rush or puzzle battle is 1800. Why is there this discrepancy and what can I do to remedy it?
Let's take another example, learning openings. What is the importance of learning an opening, and what benefits does it confer beyond those that a solid grasp of how to develop already do?
third and finally, playing through and studying a master game (or several) is all very well, but what can I do to make sure that I am able to learn lessons from a master's sometimes obscure moves, or, more importantly, that I am able to apply these lessons in the arguably very dissimilar of a real game?
Please don't take my questions as criticisms. I'm genuinely trying to learn what their value is.