If you create a report in CR 8.5, can you open it in CR 8.0?

Yes, and you can open v8 reports in v7, although some features are not
supported (different formula syntax, cross tab formatting etc).  As v8/8.5
allows you to copy multiple objects and v7 doesn't, if I am working on a v7
report, I often open it in 8, copy my fields and then take it back to v7.

Alison