The versions of Unity Engine have changed and improved significantly with each release:

● Unity 3.5: one of the great releases from Unity Technologies.
● Unity 4: included improvements in 3D textures and graphics for mobile and smartphone games, among others. It was compatible with both Microsoft DirectX 11 and Linux.
● Unity 4.3: included the new Dopesheet; setting, based on keyframes in the animation window to animate a sprite. Also, Mecanim, to boost forms of facial animations mixes.
● Unity 5.6: new 2D Toolkit enhancements, performance enhancements (Vulkan implementation), cinematic tools, virtual reality (VR) and augmented reality (AR) enhancements.
● Unity 2017: timeline and Cinemachine are added, tools that can be exploited by film, TV and animation producers, and natively in cinematics for video games.
● Unity 2018: internal improvements to its core.
● Unity 2019: performance improvements to be able to work better and more smoothly in the Unity editor.
● Unity 2020: important improvements in both 2D and 3D, as well as in the improvement of the behaviour of particles such as water and fire.