>a-how can i do this action at last row in any column ?

Does the grid property AllowAddNew help?

>b-how can i cancel this action via press UpArrow if didn't change any field at this row (same way this recno) and the record didn't buffered ( form is PrivateDataSession,Pessimistic,buffer mode 5)

You'd need to revert that record. How you'd do that depends on how you are or are not buffering your data. If you're using table buffering (recommended for tables) you can tablerevert just the one row.