Unity 4.0 was officially released o

Unity 4.0 was officially released on November 13, 2012. Major new features include new 'Mecanim' animation system, DirectX 11 support and real-time shadows on mobile platforms.[28]

With the release of Unity 4.0, the company announced a shift towards a release cycle which would see versions be released with fewer features but at a faster rate.[29] As such, subsequent releases in the 4.X line delivered new features as follows:

Unity 4.1, released March 13, 2013: Memory profiling, support for AirPlay on iOS, and a slew of smaller feature updates for Mecanim and shader editing.
Unity 4.2, released July 22, 2013: Support for Windows Phone 8, Windows Store and BlackBerry as publishing platforms; OpenGL ES 3.0 support for mobile platforms; integrated version control support for Perforce; and the ability to cancel the build process once started. (The last of these got a round of applause when it was announced at 2013's Unite Nordic).
Unity 4.3, released November 12, 2013: a new 2D framework, including both 2D rendering support and a 2D physics engine (powered by Box2D).
Unity 4.5, released May 27, 2014: no significant new features were introduced, as instead this release focused on fixing bugs, reporting more than 450 fixes in the release.
Unity 4.6, released November 26, 2014: a new UI Framework. Also, version 4.6.2, released on January 29, 2015, added support for 64-bit applications on iOS.
On May 21, 2013, CEO David Helgason announced that the 'basic' editions of the iPhone and Android mobile add-ons would now be available for free from Unity 4.2 onwards.