Hi Guru,
As you are using CR 2013 reports with an application developed with CRVS_13, because there is no SDK for CR 2013, in the same way you could use CR 2013 reports with CR 2008 .NET SDK (12.0) because this is the only version compatible with VS 2008.
This will work, But I would not suggest you to go backward (from Cr 2013 to CR 2008).
VS 2008 is only supported with CR 2008. CRVS_13 is not supported with VS 2008 and will not work.
Best approach would be to upgrade the version of VS also to VS 2010/2012/2013 and then use CRVS_13.
Thanks,
Bhushan