No. You can only use the Customer Number you received at the time of purchase only with the version you purchased. Customer Numbers are version-specific and cannot be used for other versions.
Entering a Customer Number from an older or newer version of Final Draft will not convert the existing installation to that older or newer version. All it will do is return an Invalid Customer Number error.
These are the correct Customer Number prefixes for each version:
- KFD -- FD12
- EFD -- FD11
- XFD -- FD10
- 9FD -- FD9
Only a KFD Customer Number will activate FD12, only an EFD number will activate FD11, and so on.
Also, changing the prefix of a Customer Number from one version to another will render that Customer Number useless. For example, changing the KFD in an FD12 number to XFD won't turn that FD12 number into a valid FD10 number.