Are you talking about a vendor app, because it's unlikely the database has a restriction.
If the vendor says "install Crystal 8.5 because that's what works with our product", then they may need to provide that to you. This has been the case with us.
If this is not a situation of a vendor requiring a certain version, please inform as to what database you are using that will not allow a higher version of Crystal. 8.5 is very old at this point so I might assume that your db engine is also old and potentially obsolete?