I would just email them or go into their office. You don't need to have been their TA or crazy close to them, but I would say try to use professors you have had two or three times who know who you are.

Like I said, you don't have to be close to them, but as long as they know you are a good student, that can be enough basis for a letter. Also, don't count out recommendations from other settings like a job or a coach. While yes, you want at least one recommendation from a professor, a boss or coach has likely been around you more and can offer a better view of who you are as a person through work ethic or teamwork and may be able to write you a great recommendation!

My friend just got into her dream law school and was able to speak to someone in admissions who looked at her application and she was told her best letter of rec came from her old cheer coach.

Someone correct me if I am wrong but context itself has no argument. For example, the sentence, "The toy stores in the mall are all storing damaged toys in their storage rooms," is context, but there is no argument being made. It is just a statement. We are not trying to be convinced that the toy stores have been placing damaged toys in their storage room, we are just being told that this is happening.

Now for a contextual argument, the text is trying to convince the reader of something. For example, in this text, "The character Aladdin, first introduced in the eponymous 1992 Disney movie, has become a beloved figure in pop culture. Given his well-known status and several reiterations of his story, one might presume that there is nothing else to reveal about this character." The sentence is trying to argue that many assume there is nothing to reveal about Aladins character as his character is already established in the movie. While this is an argument, it is being used as context to set up a later argument. That is why it is a contextual argument instead of just context.

I hope this helped a bit.

Honestly, it depends, but usually in the LSAT, it will flat-out tell you. For example, it usually says something along the lines of, "Assuming X is true..."

At least, that is what I noticed.