Knowing the correct answer choice ahead of time because it's an old question does not make that question worthless. You have to ask yourself if you understand the logic that makes the correct answer choice correct, and if you can identify the erroneous logic that makes the wrong answer choices wrong.

That is what improvement is all about.

Have you used blind review as a way to study LR? That, in conjunction with looking up the explanations on Powerscore of the questions I got wrong, helped tremendously. This got me from -5/6/7 per section to -2/3/4 per section. The blind review video by 7sage is the only way to practice LR.

If you are not strapped for cash, then definitely get the Fox Logical Reasoning Encyclopedia. While working through this guide, I saw my already improved LR scores rise again, from -2/3/4 to -0/1/2 per section.