I am a Junior in high school and always assumed that you could ask any teacher you want to write your recommendation and hopefully they’d say yes. Sometime when I was on this board, someone said elective teachers don’t count as teachers? I honestly have no idea if this is true or not and I never thought to even wonder. I’ve had the same French teacher for three years, so I figured she’d be a good person to count but would she not count as a recommendation?
Depends on the college, some will specify and say one STEM and one arts teacher for example. Others might just say two teachers from core subjects. Others may not specify at all. Typically though, you can add extra letters if you have one that you think would be really good.
You should check the website of each college you apply to and see if they have any guidelines as to who the recommends should be and how many teacher recommendations they want. French is generally considered to be a core academic subject so a LOR from a French teacher should be fine in most cases.
If you add an additional or supplemental letter as suggested above it is normally from someone who knows you in a non-academic setting (ex. a coach, boss etc.). This is not necessary to do.