I agree with everyone else. They lied to you once and they sold a car that was on deposit. I have NEVER heard of that being done in ANY sort of commission based job. You put a deposit down on THAT car it basically does become YOUR car once you leave a deposit down.
It depends on what you want to do, you can simply ask for your deposit back and go elsewhere but that means you'll be allowing whatever jerk that sold your car to screw someone else over. If you want the demo car because you ended up like whiteout more than firestorm then demand for either an extended warranty or a huge price reduction because demo cars are basically pre-owned by the time their done with.
After what the "manager" did, you have all the leverage in the world to demand whatever you want. Especially if you gave them cash or deposit check that they already cashed. The dealer might just not deal with you though and just return your deposit. Either way, you have nothing to lose and try to milk as much as you can from the dealer. Try to get a brand-new Firestorm sent over with Bespoke included.