What is the upgrade path for Fortis?

Answer:
The following is the upgrade path for Fortis
1.12.0 - 2.0.1 - 2.1.0 - 2.2.0 - 2.3.0 - 2.4.1 - 2.4.2 - 2.5.0 - 2.6.0 - 2.7.0 - 2.8.0 - 6.8.0 - 6.9.0 - 6.10 - 6.11

Alternatively, now after Fortis 6.10 release:
1.12.0 - 2.0.1 - 2.1.0 - 2.2.0 - 2.3.0 - 2.4.1 - 2.4.2 - 2.5.0 - 6.11

Please see the Legacy Supported Environments for details on which OS and database engine were supported at each Version.