Ehi @craaaft
happy to hear from you and welcome among the NethServer Tribe! 
you can look to some discussions here about Office 365
Moving from office365 to NethServer at school - #7 by mabeleira
coming back to your questions
- not currently but it’s very requested, obviously in the meantime you can obtain the same result playing with rsync or duplicity following this topic Backup-data-cloud by @filippo_carletti
- we recommend the NethServer 6.7 or at least CentOS 6.7, btw NethServer 7 alpha2 is coming
- no, but wnCloud includes the versioning support that as far as I know is pretty similar.
- clamav is already built-in, do you need anything else?
Happy to read this, stay around, make this your place, share your plans and goals and offer your feedback on what happens here.