Eval license as such includes antivirus and antispam options, file filtering is not license limited option.
Virtual context indeed do not support antispam. Antivirus was moved under File filtering in 5.8 and thus starting from 5.8 version antivirus is available for virtual context. With earlier versions antivirus either was not supported on virtual context.
It's also good to distinguish terms virtual appliance and virtual engine from each other. Virtual appliance term is used of an engine that you can run eg. on ESXi and virtual engine term is used of an individual engine under a master engine (virtual contexts).