Hi,
I don't quite understand your question, you're mixing versions for two different softwares - Joomla and JoomSEF.
Joomla 1.5 requires JoomSEF 3.x, Joomla 1.7 and 2.5 requires JoomSEF 4.x.
If you have Joomla 1.5 with JoomSEF 3 and want to migrate to Joomla 2.5 with JoomSEF 4, even though you can import your URLs and meta tags from JoomSEF 3 to JoomSEF 4, but due to different URLs structure in Joomla 2.5, we can't guarantee that the URLs will work correctly. So it's usually better to configure JoomSEF 4 from scratch to generate the same SEF URLs as JoomSEF 3 did.
