Unity 2017.4 is the LTS release, containing features released in 2017.1 to 2017.3. Unity intends to support this version for 2 years. For more information, see the Tech & LTS streams blog post and the LTS release page.
Follow the links below to find User Manual pages on new and updated features in Unity 2017:
New in Unity 2017.3
New in Unity 2017.2
New in Unity 2017.1
These pages list the corresponding version’s new and updated User Manual pages, detailing the following:
To find out more about the new features, changes, and improvements to Unity 2017 releases, see:
2017.4 Release Notes
2017.3 Release Notes
2017.2 Release Notes
2017.1 Release Notes
If you are upgrading existing projects from an earlier version of Unity, read the Upgrade Guides for information about how your project may be affected.