I will try to answer your questions in one post.
I have attached a project with the default style of the RadListViewItem, which you can modify to customize the appearance of the items.
If you are grouping by a string value, then the groups will be ordered lexicographically. If you wish to order them by the actual DateTime value, then you can use a property of type DateTime. I would like turn your attention to the fact that the context of this thread is not related to your issue. If you have further questions, I would like to kindly ask you to open a new thread. This will help us to better handle your case.
I hope this was helpful. Please, let us know if you have any other questions.
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Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Feedback Portal
and vote to affect the priority of the items