RTFM afterview

Instead of posting countless questions I will just post remarks as answers so that readers can follow along and get insight to complex lines of code and calculations.

I would like to use the scripting manual to dissect this statement: Vector3.Cross(rigidbody.angular.velocity, Vector3.up).normalized;

As I type this line the next dot item is missing either in case sensitivity or all together.

So there is discontinuity across the Unity product.

I'm not sure where you get this line of code, but if it's from the documentation you've just found a mistake. A Rigidbody component doesnt have something like "angular". To get the angular velocity of the rigidbody the required property is called "angularVelocity"

I'm still not sure if you understand what a "dot" actually does. The dot tells the compiler to access a member of the object/struct in front of the dot. The rigidbody is actually a property of Component which allows you to easily access the Rigidbody component of the GameObject this script is attached to.

rigidbody will return the reference to a Rigidbody component but only when such a component is attached to the GameObject, otherwise it returns null. If you take a look into the documentation to Rigidbody you can see all members variables/ properties and methods you can access.

ps. if you want to add details to your question you should use the "edit" button below your question or use comments.