v10 and v11.5 compatibility

Hi all,
Hope this isn't a stupid question but here goes anyway.
I have many backups in v10 and recently upgraded to v11.5. I have upgraded a few of the backups to this new version but have many I haven't yet. 11.5 sees older backups and will recover them but if I recover a v10 backup (which has v10 in the image) and then try to recover a v11.5 backup I can't even see the new backups (I thought I somehow lost them all). If I use the boot CD I can see them and recover them. So the two diffferent versions are not compatible?