Most of this stuff isn't very difficult to find on the internet if you know where to look!
I googled "Octopus vulgaris temperature range" and the first link was to wikipedia which said 59F to 61F, which is a pretty reasonable range. You could also google "octopus vulgaris range" and the first result was an excerpt from "marinebio.org" which says they live in various waters around the Mediterranean sea, off the coast of japan and elsewhere, typically at a depth of 1-200 meters. Google even highlights this information at the top of the search! I didn't even need to visit the marine bio website.
Ill leave it to you to google "temperature of Mediterranean sea 200 meters" for more information pertaining to their habitats' typical temperature range.
The chromatophores are most heavily present on the skin of the octopus, so I suppose that's the "main body system affected by the usage of the chromatophores"
Your last two questions are the most interesting ones, and the ones that require the most research. Rather than telling you the answers I'll give you a few things you can google to help yourself. I like to use google scholar to answer these kinds of questions, especially for something like a school project. The first thing I searched was just "Octopus vulgaris chromatophores" which yields a few good results. Looking at paper titles alone, I would check out the paper by JB Messenger found
here. You could also take a look at
this paper published in the 70's. Depending on how thoroughly you want to answer your questions, you could probably start by reading the paper abstracts and seeing if there is relevant information there for you, you probably don't even need to read the entire paper from start to finish.
If you are having troubles accessing any papers online, I would reach out to your schools IT department or library, they may be able to help you.
Ultimately, doing a few different searches on google scholar will likely get you the answers you want. Let me know if you are still having trouble finding answers, but this is pretty common information and I don't think you will have much trouble after you spend some time digging around on the internet.
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