If you need the specific behavior of version 1.2 for a legacy project, consider opening the project in a newer After Effects – it will usually convert the effect settings automatically.
Users with very old versions (like CS2 or earlier) might lack Keylight. However, those versions are obsolete and won't run on modern operating systems. Upgrading to a current version of After Effects (even via a monthly subscription) is the only safe route. after effects keylight 1.2 download