SQL & PL/SQL

I have the following situation:

DECLARE
   text   VARCHAR2 (100) := '';
   
   TYPE gen_cursor is ref cursor;
   c_gen gen_cursor;

   CURSOR c_tmp
   IS
        SELECT   *
          FROM   CROSS_TBL
      ORDER BY   sn;
BEGIN
   FOR tmp IN c_tmp
   LOOP
      text := 'select * from ' || tmp.table_name || ' where seqnum = ' || tmp.sn;

      OPEN c_gen FOR text;

      -- here I want to iterate over the columns of c_gen
      -- c_gen will have different number of columns every time,
      --        because we select from a different table
      -- I have more than 500 tables, so I cannot define strong REF CURSOR types!

      -- I need something like
      l := c_gen.columns.length;
      for c in c_gen.columns[1]..c_gen.columns[l]
      LOOP
          -- do something with the column value
      END LOOP;
   END LOOP;
END;

As you can see from the comments in the code, I couln'd find any examples on the internet with weak REF CURSORS and selecting from many tables.
What I found was:

CREATE PACKAGE admin_data AS
   TYPE gencurtyp IS REF CURSOR;
   PROCEDURE open_cv (generic_cv IN OUT gencurtyp, choice INT);
END admin_data;
/
CREATE PACKAGE BODY admin_data AS
   PROCEDURE open_cv (generic_cv IN OUT gencurtyp, choice INT) IS
   BEGIN
      IF choice = 1 THEN
         OPEN generic_cv FOR SELECT * FROM employees;
      ELSIF choice = 2 THEN
         OPEN generic_cv FOR SELECT * FROM departments;
      ELSIF choice = 3 THEN
         OPEN generic_cv FOR SELECT * FROM jobs;
      END IF;
   END;
END admin_data;
/

But they have only 3 tables here and I have like 500. What can I do here?

Thanks in advance for any help!