Ignore the above post.
Please follow the updated post.
5.2.3 --> 5.2.4 --> 5.2.5 --> 5.2.7 --> 5.2.9 then according to the Upgrade Path Tool to 6.0.14.
Also, go through release notes of 6 series firewall you are planning to upgrade to (To have clarity about new features, known and
resolved issues detailed)