Answer 1: First you have to call REST API using the  fetch() method. Then, you can access the response data using the promises with the fetch() method. The data from the response is saved to the state and the component is re-rendered when the state has changed.

Answer 2: You have to send a DELETE method request using the fetch() method. The endpoint of the call is the link to the item that you want to delete.

Answer 3: You have to send a POST method request using the fetch() method to the entity endpoint. The added item should be embedded in the body and you have to add Content-Type header with application/json value. 

Answer 4: You have to send a PATCH method request using the fetch() method.  The endpoint of the call is the link to the item that you want to update. The updated item should be embedded in the body and you have to add Content-Type header with application/json value.  

Answer 5: You can use some third-party React component to show toast messages like React Toastify.

Answer 6: You can use some 3rd party React component to export data to CSV file like React CSV.