All three cuts are included on Disc One, presented in with a 1.78:1 aspect ratio:
The Extended Cut begins with Jake Sully on a dystopian, futuristic Earth. While some viewers feel this slows the initial "flow," others argue it provides critical context for his desperation to escape his life and his growth as a character. avatar2009extendedcollectorsedition1080
The official product is from 2010. Look for the black box with the lenticular slipcover. Used copies pop up on eBay, and the discs are region-free. If you see avatar2009extendedcollectorsedition1080 in a file-share context, it likely points to a remux of that exact release. All three cuts are included on Disc One,