The first one I think is a Grimpoteuthis "dumbo" octopus, they are deep sea and cannot be kept as pets if that's what you are wondering. The rest I am unsure.
#2 given the photographer, likely a native of Australia or Maldives.
#3 is a hatchling in an aquarium setting. The source of the photo should have the species.
The last is Octpus marginatus or commonly called the coconut octopus. Small but not dwarf/pygmy. I would love to keep one but we MAY have seen one on the forum since I have been a member.
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