Is this appropriate for the "Additional Info" section?

I am considering adding some info to the additional info section.

I have three things that I am considering covering, but I am not sure if they are a good idea to put them there.

Idea 1: Spanish 3
I have had straight A’s in 10th and 11th grade.
9th grade I have a B in Spanish 3, and an A- in algebra 2.
I don’t necessarily want to justify why I got a “B” but I genuinely feel that failing in that class was the most influential class on my entire transcript. I am considering explaining how she was a new teacher with high expectations. The class average was low, and it took a lot of effort to get a passing grade. I learned more in Spanish 3 then in Spanish 1, 2, or 4.The class grew me more than any other class because I was forced to develop better study techniques. I realized I can not just expect talent to get me through classes.

Idea 2: Cycling
I really love biking, and do it in a lot of my free time because it is my escape from being academic, it gives me space to think. My area does not have a club so I can’t put it in activities, but I can’t wait to do it in college.

Idea 3: Self-taught programmer
My school really only has basic programming classes. I exhausted those rather quickly and would usually finish all the class material within the first month. As a result I am a self-taught programmer. I have spent years reading textbooks, using online tutorials, etc. I have learned many programming languages, figured out how to design game engines from scratch, learned opengl graphics programming, made apps.
This would be slightly redundant as I have an activity listed that sorta touches on this just not with as great of a list or explanation as to why.

I’d put biking & programming in activities with the hours you spend. I would not make any attempt to make excuses about grades in additional info. So in summary, I would not put any of these in additional info.

^agree with above

OK your rationale makes sense. Also, I realized while reading through my application that I never explicitly stated that I have been a piano student for 14 years and a cello student for 6 years. Instead I listed activities that apply those skills. Would that be something to include in the additional info section since it did not fit or feel appropriate in the activities section?

You can put a one sentence explanation if you want to in additional info. Do not write an extra essay, be concise.