Oracle 18c

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CREATE TABLE tab(
                 key_col INT PRIMARY KEY, 
                 col_a   VARCHAR2(25), 
                 col_b   VARCHAR2(25), 
                 col_c   DATE,
                 col_d   INT
                )
INSERT INTO tab
SELECT 1, 'a', 'b', date'2020-07-07', 23 FROM dual UNION ALL
SELECT 2, 'x', 'y', date'2020-07-08', 46 FROM dual 
2 rows affected

DECLARE
  val  VARCHAR2(4000);
  tbl  VARCHAR2(40)  := 'TAB';
BEGIN
  DBMS_OUTPUT.PUT_LINE('KEY_COL    COLM      VALUE ');  
  DBMS_OUTPUT.PUT_LINE('-------    -----     ------'); 
  FOR c IN (  
              SELECT t.*, c.* 
                FROM user_tab_columns c
               CROSS JOIN tab t
               WHERE table_name = tbl AND column_id > 1
               ORDER BY t.key_col, c.COLUMN_ID  
           )
  LOOP 
      EXECUTE IMMEDIATE 'SELECT '||c.column_name||' FROM '||tbl||' WHERE key_col = :kc' 
                   INTO val 
                  USING c.key_col;  

      DBMS_OUTPUT.PUT_LINE(c.key_col||'          '||c.column_name||'     '||val);      
  END LOOP;
END;   
/
1 rows affected

dbms_output:
KEY_COL    COLM      VALUE 
-------    -----     ------
1          COL_A     a
1          COL_B     b
1          COL_C     07-JUL-20
1          COL_D     23
2          COL_A     x
2          COL_B     y
2          COL_C     08-JUL-20
2          COL_D     46