Straight to the points:
1. You can access the header item during the PreRender event handler of the grid and traverse and hide the mentioned TableCells by using their Visible="false" or .Style["display"]="none" property. However, please note that this requirement is not tested and may prove error-prone.
2. You will need to pass a valid DataSourceID to the inner grid as demonstrated in the following live sample:
Alternatively, you can use programmatic databinding with the DataSource property, similar to attached web site sample.
I hope this will prove helpful.
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