No, Final Draft 12 requires a Customer Number that starts with KFD. Replacing the first number or letter of the Customer Number from a previous version with a K does not make it a valid FD12 Customer Number.
If you have downloaded and installed FD12 but have not purchased the upgrade to FD12, you have a read-only version of the program and you will not be able to write or edit scripts.
There is no free upgrade to FD12 from previous versions of Final Draft.
If you are interested in upgrading, log on to https://store.finaldraft.com/final-draft-12-upgrade.html or contact our Sales Department at 818-995-8995, 8:30AM - 5:30PM PT M - F.