Salopette Questions?

Hello everyone! I recently purchased an AP Cotton Candy Shop Salopette Lucky Pack, it's quite cute and it fits wonderfully. But I do have a couple questions about Salopettes in general/personal. If any of the questions seem completely obvious, I apologize! I'm still trying to learn the ins and outs and dos and don'ts of lolita for I am quite new to the fashion.

- I have seen around that some say Salopettes aren't part of lolita, but more part of the Fairy-Kei fashion or other types of fashion. Is this true?

- Are Salopettes like JSKs? Or are they a type on their own?

- Do you need a petticoat? I know that in lolita it is an absolute must but some have been saying you don't need one or it just depends.

Now to the sort of related personal question:

Even though the Salopette fits wonderfully, I am 5'5" and the skirt is well over my knee. Is this normal for a Salopette? I know that according to lolita guidelines skirts cannot be over 2" above the knee (but there are exceptions to some styles). Will I have to get an underskirt to lengthen it?

So those are my questions. Again I apologize if some answers are obvious or some questions overlay one another.

If I'm not clear enough please let me know!!