Can't restore from TM backup in recovery mode
On a 2012 MacBookPro the network boot image is Mavericks and that results in the messages reported by the OP when attempting a restore. Rather than performing a full install as suggested above, all that's needed is to create a High Sierra bootable USB as per https://support.apple.com/en-gb/ht201372, boot from the USB, and immediately select "Restore from a Time Machine Backup". The restore from a High Sierra boot works, whereas the Mavericks one does not.