I am trying the following customization for the PolarArea chart and only the legend part works. Can anyone review the following and tell me why it doesn't work?
Those are properties of the dataset. You cannot reach them via ui_control message. To modify them, you'll need to create the chart from scratch using the ui_template node. (Or template node feeding ui_template).
You can find many examples here in forum where chart is created that way but I'm afraid none of them will have Polar Area Chart. But anyway - it is basically same just you'll need to follow documents to create needed structure for polar chart.
It takes kind of intermediate understanding of front-end codding.