Thank you for contacting us. I am not sure I understand the first issue completely. Typically, if you do not want to let the user modify a column, you should set the ReadOnly property of that column to True. Here is sample code how to do that:
Please, note that an issue with setting the ReadOnly property of the RadGridView columns was introduced in Q2, however, the issue was resolved immediately in Q2 SP1. So, please, upgrade your project to Q2 SP1 and let me know the result.
About the second question, you are right that there is no default context menu for the RadChechBoxCells. If you want to have a context menu, you need to assign a custom one. You will find more information how to achieve that here. I have also attached a sample project that demonstrates how to attach the custom RadContextMenu to RadChechBoxColumn. I hope this is helpful. If you have further questions, please, contact me back. Best wishes,
the Telerik team