VPP Composition is available today in Windows and Linux. You can download the samples from here and sample_vpp example shows how to add composition. https://software.intel.com/en-us/intel-media-server-studio-support/code-samples
Please see this thread as well - https://software.intel.com/en-us/forums/topic/540105
On 3rd gen - No, VPP composition was not available. We recommend developers to implement the SW version of composition here.
Hello there - The latest API available for Windows is 1.15 - so if you can download that version (the install process installs the required driver as well), that will work for composition.