This feature is available in all editions.
If an item is deleted by mistake, in most cases (some item types such as list values or custom fields cannot be undeleted) you can use Undo Delete to reverse the deletion and bring it back into the system. Any previous relationships will be re-established with the undo delete, including any links and attachments, child tasks/tests, etc.
If you undo the delete of an item that caused cascaded deletes down to child items (e.g. tasks, tests, links or attachments), Undoing that delete will restore the child items that were deleted at that same time.
Option 1. In Recent Changes
All of your deleted items display in your Recent Changes list. So, if you realize just a bit too late that the item you just deleted shouldn't have been, it can be viewed and accessed from that list.
Option 2. Using Advanced Search
The Advanced Search allows you to search for an item that may have been deleted by mistake by you or anyone else. So, in cases where you don't know who deleted the item or just have a feeling that something used to be there and is no longer, you can just enter your search criteria and select Deleted from the advanced search page to return any deleted assets that match the search criteria.
Option 3. Using the API
Deleted items can also be viewed through an API query. Below is a query example that would return all deleted backlog items in XML format.
Be sure to replace this portion of the URL:
to match the initial URL of the Lifecycle system that you use. The query above can be further refined by adding a 'where' clause, or by selecting certain attributed to be returned. Please see the community article, rest-1.v1/Data for more information on how to refine your query.