The following query will give you almost what you want, if you supply the ID for the Requirement that is the parent.

with ReqCTE
as
(
SELECT
REQ.RQ_REQ_ID,
REQ.RQ_REQ_NAME,
REQ.RQ_FATHER_ID,
0 as lvl
FROM
td.REQ
where
REQ.RQ_REQ_ID = {?Father_ID}

union all

select
Folders.RQ_REQ_ID,
Folders.RQ_REQ_NAME,
Folders.RQ_FATHER_ID,
Child.lvl +1
from
ReqCTE as Child
join td.REQ as Folders on Folders.RQ_FATHER_ID = Child.RQ_REQ_ID
)
select * from ReqCTE

The output will look something like this

RQ_REQ_ID RQ_REQ_NAME RQ_FATHER_ID lvl
1309 Parent 1312 0
1310 Child 1 1309 1
1311 Child 1.1 1310 2
1314 Child 1.2 1310 2
1315 Child 1.1.3 1311 3