I usually run nitro helis and trucks, I bought a heli that uses 11.1v batteries. I see most cars run 7.2 volts. Are there any that run 11.1v?

Lots of them can use 11.1

Depending on your ESC, Most 1/10th scale ESCs can support up to 3S. And mostly 1/8th scale ESCs can support to 6S.

If your ESC does not have a lipo cut off feature, you will need to buy an external one.

11.1 is typically a battery pack for a 1/10 scale basher. anything higher than 3s is usually in a larger scale vehicle.