By default, Telerik OpenAccess ORM generates dynamically the SQL statements used for CRUD operations. The "Use Stored Procedures" option enables you to select a stored procedure which can be used to override the automatically generated SQL. The stored procedure can be created by OpenAccess as well, if necessary. For more details on how to achieve this, please take a look at this help topic
Regarding your second question, it is not possible to automatically create Add / Edit / Delete methods in the class definition, as this functionality is handled by the IObjectScope. However, by using the option described above you are getting almost the same behavior - each class can use different stored procedure for particular write operation.
the Telerik team