For example if I have to disable SO 'Delete' function through security (not through parameter control) on disallowing users to delete INVOICED SO. May I be advised how I can do so?
Thanks in advance.
No, you don't need any development. Simply set Safety level of invoiced orders (in Accounts receivable parameters) to Locked.
Then how would restricting the deletion of invoiced for some users address your concern? To achieve this, you may have to go for the customization, so that it will not allow the delete but still will allow you to create the credit note.