Yes? Some of your backups will be the encrypted version of the file. As long as your system remains hacked it is useless to restore anything. You will first need to purge every disk in your organisation and reinstall everything from scratch (depending on the sophistication of the ransomware, maybe just buy new disks altogether), THEN restore from a version that is good.

Yes, but backing up from an infected system is probably not a good idea. Better to mount the drives on a different system, and backup from there.

That's why you use WORM Tapes and versioned files if its really important data.