How to control the specified wheel steering?

I have created a car that has four wheels, and I want to achieve a function that I can control the special wheel to steer.
For example: I input a steer value, the front wheel turn left, the rear wheel turn right. Or I input a steer value, there only one wheel can turn. But now I don’t know how to do that.
Who can provide me with some ideas? I look forward to your answers.

I find answer! ! !
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