The phrase "first preview" refers to the initial showing or demonstration of something before it is officially released or made available to the public. Full definition
This was the fabled first preview of the new Nvidia Tegra 3 Quad - Core processor, dubbed Kal El. (goodereader.com)
I Will Be is an evocative ballad, while her rendition of Stand By Me, as first previewed at the UNCOVERED: FINAL FANTASY XV event in March, gives the Ben E. King classic a beautiful, melancholy edge. (thebuttonsmashers.com)
The harrowing first preview for The Birth of a Nation charts Turner's story from a preaching slave to the leader of a rebellion that fought for freedom as well as the atrocities Turner witnessed along the way. (rollingstone.com)