except (sampler track) I have this question because I have some collaboration with a friend who is using 8.5
its possible to open projects done in 9.5 in to 8.5?
yes
Yes… the project itself will open but keep in mind that CB 9 and later dropped 32 bit vst support. This might pose some hassles when collaborating.
Regards. 
One of the thing that probably won’t come down is the chord track/arranger track. Can’t remember which one doesn’t. The data gets erased. So don’t bring it down to 8.5 and save.