Form continous chain from a table SQL?

Question

Consider the following SQL table (#forming):

SeqNo	StartStep	EndStep
788	A	B
788	A	C
795	B	C
797	C	D
798	D	F
798	D	G

Chain 1 : A  TO  B  TO  C  TO  D  TO  F 
Chain 2 : A  TO  B  TO  C  TO  D  TO  G 
Chain 3 : A  TO  C  TO  D  TO  F 
Chain 4 : A  TO  C  TO  D  TO  G 

Expected output: So it would return all the above rows i.e. a total of 14 rows because of all the combinations:

SeqNo	StartStep	EndStep
788	A	B
795	B	C
797	C	D
798	D	F
788	A	B
795	B	C
797	C	D
798	D	G
788	A	C
797	C	D
798	D	F
788	A	C
797	C	D
798	D	G

Another example,

SeqNo	StartStep	EndStep
823	A	B
826	B	C
826	B	D
826	B	E
827	D	F
827	D	E
836	E	C
837	C	G

Chain 1 : A TO B TO C TO G

Chain 2 : A TO B TO D TO F

Chain 3 : A TO B TO D TO E TO C TO G

Chain 4 : A TO B TO E TO C TO G

EXPECTED OUTPUT

SeqNo	StartStep	EndStep
823	A	B
826	B	C
837	C	G
823	A	B
826	B	D
827	D	F
823	A	B
826	B	D
827	D	E
836	E	C
837	C	G
823	A	B
826	B	E
836	E	C
837	C	G

Answer 1

WITH 
cte1 AS (
    SELECT *, 
           DENSE_RANK() OVER (ORDER BY SeqNo) dr,
           ROW_NUMBER() OVER (ORDER BY SeqNo) rn
    FROM test
    ),
cte2 AS (
    SELECT SeqNo, StartStep, EndStep, CAST(',' + StartStep + ',' + EndStep + ',' AS NVARCHAR) path, rn, 1 sn
    FROM cte1
    WHERE dr = 1
    UNION ALL
    SELECT cte1.SeqNo, cte1.StartStep, cte1.EndStep, CAST(cte2.path + cte1.EndStep + ',' AS NVARCHAR), cte2.rn, cte2.sn + 1
    FROM cte2
    JOIN cte1 ON cte2.EndStep = cte1.StartStep
    ),
cte3 AS (
    SELECT rn, MAX(sn) sn
    FROM cte2
    GROUP BY rn
    )
SELECT test.SeqNo, test.StartStep, test.EndStep
FROM cte2
JOIN cte3 ON cte2.rn = cte3.rn
         AND cte2.sn = cte3.sn
JOIN test ON CHARINDEX(',' + test.StartStep + ',' + test.EndStep + ',', cte2.path) > 0
ORDER BY cte2.path, test.SeqNo
;

https://sqlize.online/sql/mssql2017/ec39e9511c9ee3751981a6f2bc94381c/