I can assure you that octos can see through both acrylic and Plexiglas, and I don't have a reason to believe they cannot see through other kinds of plastic as well. I've done some interesting experiments with octopuses reaching through holes in acrylic sheets to grab crabs. The main motivator for their reaching behavior seems to be their internal state (hungry/satiated/agitated/etc.) so if your animal is eating every day, they will probably not be very motivated to "work" for their food, especially if they are used to hunting in their tank, rather than unscrewing jars.