Necessary Theory

What are some openings/variations you need to know how to play against?

Opening principles will cover every opening.

at an certain level you can use opening principles, but you are without the knowlegde of it very vulnerable to opening traps and dont know what to do in the middle game. Means you have no strategical or positional ideas.

Opening principles got me to USCF A class. But to each their own on what and how they want to study. When it comes to opening study. Memorizing moves is useless without any understanding why those moves are made. You will make much better progress by understanding the pawn structures that go along with the openings you decide to play. But again. Play, study, etc that makes the game fun.

Thanks for the information🤯🤯🤯🤯🤯🤯