SQLite: Duplicate row n times to the end of a table, but with some altered data?

Question

I have a table called 'scenes'...

id   created       modified      scene_id
------------------------------------------
1    1999-11-31    2000-01-27    ABCD
2    2000-12-31    2001-01-27    EFGH
3    2001-12-31    2002-01-27    IJKL
4    2002-12-31    2003-01-27    MNOP
5    2003-12-31    2004-01-27    QRST

...what I'm trying to do is to duplicate a row (line 2 in this example) at the end of the table n times (4 in this example), but also alter the scene_id to give them unique identifiers. This is a shortened explanation, but the original is a large table with about 50 columns, and I want to split some of the rows into separate parts, to get something like this:

id   created       modified      scene_id
------------------------------------------
1    1999-11-31    2000-01-27    ABCD
2    2000-12-31    2001-01-27    EFGH
3    2001-12-31    2002-01-27    IJKL
4    2002-12-31    2003-01-27    MNOP
5    2003-12-31    2004-01-27    QRST
6    2000-12-31    2001-01-27    EFGH-A
7    2000-12-31    2001-01-27    EFGH-B
8    2000-12-31    2001-01-27    EFGH-C
9    2000-12-31    2001-01-27    EFGH-D

I first saved some of the information in a temporary table called 'variables'

CREATE TEMP TABLE variables (
    scene_id TEXT, 
    num_files INT,
    scene_index INT
);
INSERT INTO variables VALUES (
  'EFGH',
  4,
  2
);
SELECT * FROM variables;

scene_id    num_files   scene_index
------------------------------------
EFGH        4           2

I also stored line 2 in a table called 'dupedScene'

CREATE TEMP TABLE dupedScene AS SELECT * FROM scenes WHERE id = (
    SELECT scene_index FROM variables
);
UPDATE dupedScene 
    SET id = NULL; -- reset id column to trigger auto increment
SELECT * from dupedScene

id     created       modified      scene_id
-------------------------------------------
null   2000-12-31    2001-01-27    EFGH

I then tried various ways to 'loop' INSERT INTO using recursive CTE and JOIN, but I'm struggling to get these things to work together. I got this far, but I keep getting general errors:

WITH RECURSIVE
counter(x) AS (
    SELECT 1
      UNION ALL
    SELECT x + 1
    FROM counter
    WHERE x < (SELECT num_files FROM variables)
)
INSERT INTO scenes
  SELECT * FROM dupedScene
  JOIN counter ON x

Any SQL masters that can help?

Answer 1

The query would be

INSERT INTO scenes
WITH RECURSIVE
counter(x) AS (
    SELECT 1
      UNION ALL
    SELECT x + 1
    FROM counter
    WHERE x < (SELECT num_files FROM variables)
)
  SELECT * FROM dupedScene
  JOIN counter ON x

But you have 5 Columns that you try to insert into scenes, but that is easily remeded

see https://www.db-fiddle.com/f/jLbLD5eiRV8gKYc4RrB6o3/0