1) I would say with 6 billion on the planet at this time some star seeds have had other lives on earth. We all have what I call our more extensive akashic memory. For the first timer here, that is what they would pull in from it, their past life.
2) Earth is the newest planet of free choice in our galaxy. My understanding is that 8 previous races have chosen evolution and some other number did not. Eternal souls like us do energy work for the creative sourse. It is a lot more than a mission. Those who are not like us watch and are curious.
3) I would say yes. My understanding is that there are indeed highly evolved dark workers from planets of free choice who chose self destruction on earth. They are here to disrupt our evolution. Just my opinion. I can not get any verification for my beliefs on this through good channeled sourses.
May I say that all eternal beings like us are from the creative sourse, which is love and benovalance. However when given free choice, some will go for that lower vibration. How that all unfolds in this greater and grander plan for this universe I do not know.