1)
Melody because I think it's really sweet and cute. I also like the spelling Melodie.
2) It goes in order of:
Melody,
Melanie and last
Mallory.
3)
Melody: soft pink or pastel colours come to mind, and of course musical notes but no inparticular instrument (except maybe a violin), she's be sweet and soft, blonde hair, maybe a little shy.
Melanie: dark, rich colours such as purple come to mind. I think of someone bold and charasmatic, funny and sarcastic.
Mallory: I've honestly no idea about this name, I just don't like the sound of it, it sounds too surname-y and black.
4) I've never met a girl with any of these names.
5) I consider
Melanie a little dated but still very usable.