How to use stack canvas in tab canvas in oracle forms and How to set the tab canvas first tab at runtime in oracle forms?

How to use stack canvas in tab canvas in oracle forms:

We write the Module Level Trigger <When_Tab_Page_Change>

IF :SYSTEM.TAB_NEW_PAGE = 'MAIN_TAB' THEN

                        SHOW_VIEW('CAN_STK_MAIN_TAB');

                        HIDE_VIEW('CAN_STK_PAGE_EDU');

                        HIDE_VIEW('CAN_STK_PAGE_EMP_DTL');

                        GO_BLOCK('XXBRAC_ADV_SRCH_HEADER_V') ;

                        GO_ITEM ('REQUISITION_ID');

ELSIF :SYSTEM.TAB_NEW_PAGE = 'TAB_PAGE_EDU' THEN

                        SHOW_VIEW('CAN_STK_PAGE_EDU');

                        HIDE_VIEW('CAN_STK_MAIN_TAB');

                        HIDE_VIEW('CAN_STK_PAGE_EMP_DTL');

                        GO_BLOCK('XXBRAC_ADV_SRCH_HEADER_V');

                        GO_ITEM ('EDUCATION_LEVEL_1');

ELSIF :SYSTEM.TAB_NEW_PAGE = 'TAB_PAGE_EMP_DTL' THEN

                        SHOW_VIEW('CAN_STK_PAGE_EMP_DTL');

                        HIDE_VIEW('CAN_STK_MAIN_TAB');

                        HIDE_VIEW('CAN_STK_PAGE_EDU');

                        GO_BLOCK('XXBRAC_ADV_SRCH_HEADER_V');

                        GO_ITEM ('CURRENT_DESIGNATION');

END IF ;

How to set the tab canvas first tab at runtime in oracle forms?

-----#############################################################-----

----- CALL the MAIN TAB every time from the Search Button Click   -----

-----#############################################################-----

DECLARE

tb_pg_id TAB_PAGE;

BEGIN

tb_pg_id := FIND_TAB_PAGE('MAIN_TAB');

                        IF GET_TAB_PAGE_PROPERTY(tb_pg_id, enabled) = 'FALSE' THEN

                       

                                                SET_TAB_PAGE_PROPERTY(tb_pg_id, enabled, property_true);

                                                Set_Canvas_Property('CAN_TAB',TOPMOST_TAB_PAGE,'MAIN_TAB');

                        --:SYSTEM.TAB_NEW_PAGE and :SYSTEM.TAB_PREVIOUS_PAGE

                        ELSE

                                      Set_Canvas_Property('CAN_TAB',TOPMOST_TAB_PAGE,'MAIN_TAB');

                       

                        END IF;

END;