I’m trying to disable shadows for my iPhone game. I want to do something that looks like chaos rings, where all of the shadows are baked into the texture.
Does the toon shader work on the iphone?
You don’t need to disable anything, as shadows are not supported on iOS at all
how about opengl 2.0 support?
OpenGL ES 2.0 support is present, but it won’t anything to shadows, Unity has no support for dynamic shadows on the mobile platforms (iOS / Android) independent of the settings.
The only kind of projection available is the blob projector
not even vertex lighting?
Don’t see how thats related. We were talking about shadows, not lighting 
You have pixel as well as vertex lighting present but no dynamic shadows.
You can implement your own planar shadows using RT in Unity iPhone but you need Unity iPhone Pro for that. Btw, shaders on Unity iPhone are currently quite slow and buggy. Better wait for future updates/fixes.
They aren’t buggy
Most people are just “lazy” and use the surface shader system or even worse, use U2 shaders which are just horrible.
But if you do real mobile shaders, which means GLSL, then they are quite fast.
Its at the time slower than going with fixed function pipeline, but not that extremely slower if you have mobile optimized GLSL that you should avoid it at any cost
You just shouldn’t use shaders if you don’t need them.
A thing thats always costly, not due to unity but just cause it is, is pixel lighting if you don’t use it carefully though