Image Line occasionally prunes very old versions. If the official 12.5.1 link is gone, you can request it via a support ticket. Never Google "FL Studio 12 Mac free download" — the top 10 results are all malicious.
If you purchased FL Studio any time after 2014, your license works on version 12. Download Fl Studio 12 Mac Os X
No license? The demo mode allows you to use every feature, but you cannot reopen saved project files. This is perfect for testing if FL 12 works on your Mac OS X machine before buying. Image Line occasionally prunes very old versions
You should Download FL Studio 12 for Mac OS X if: If you purchased FL Studio any time after
You should NOT download FL Studio 12 if: