There's a warning label that says this product contains something that can cause cancer. I was just wondering what that chemical is?

Dude. Quit disregarding what people are saying to you over and over! I live in CALIFORNIA, that's PROPOSITION 65 thing! A LOT of things are labeled like that. Maybe in YOUR state, (wherever the heck you are); they don't, but almost EVERY BUILDING you go into has sights at the entrance that say what your seeing. it is because it may be old and have lead paint underneath everything else. My apartment in Sherman Oaks has asbestos somewhere, MAYBE, because it EVEN SAYS MAYBE ON THE SIGN! I.E. 'May have asbestes, lead based paint etc ' Seriously! Every building more than 30 years old! So if you don't want to walk into ANY buildings or do ANYTHING, then go AHEAD! You're overly paranoid! Does it say 'PROP 65' on it? If it does it's because of Californias PROPOSITION 65 LAW! JUST DON'T MOVE TO OUR BEAUTIFUL STATE OF CALIFORNIA AND YOU WON'T GET SICK! LOL! Being as your hypochondriac you probably don't want to come here anyways. Were pretty mellow here! Plus! There's pockets of hippies wearing patchouli everywhere! Now THAT should be banned! Ha!

Does it fold flat? Is it double hinged for more flexibility?

It folds flat however completely flat it loses balance and tips over. It has hinges at top and bottom of that is what you meant by double hinged. I have two in my unisex salon for privacy and they serve me well

Would it be possible to install brackets to attach to a wall?

If you have not done so already, then yes, you can, I've done it for years. I've owned a 3-panel in black which started to look dingy and dirty after many years of use. I loved it so much I replaced it with a 4-panel in black. I recently purchase a new cherry bed frame and end tables and am now purchasing a 4-panel in cherry. Instead of hanging pictures on the walls in the bedroom, I remove all the hinges from the panels and hang then instead of framed pictures. It looks so good because they all match and the black screen color really pops on the wall. They look great and add a lot of interest, and, I feel, enhance the beauty of anything you set in front of the screen (lamp, flower arrangement, etc). I buy a pack of hangers that have what look like sharp teeth and tap the little nails into pre-drilled holes (I pre-drill to make it easier to hammer in those tiny little nails). I've also added embellishments at the top and bottom of the screen, the side facing the room, with brass pieces that I screwed on with little brass screws I bought at the hardware store. I've also randomly stenciled tiny bamboo leaves and stalks on a few of the panels with a tube of the water based craft paint, too.