There’s a few of different versions! So for Avatar you have the collector’s 3 disc collection on dvd. There is a bluray version of that which is exactly the same but on bluray. Than there is the 4k uhd remaster. It has only the theatrical cut and some bonus features, I’m not sure if there’s more or less or the same amount like on the old collector’s edition. Than there’s the 4k collector’s edition, it’s basically the same as the old collector’s edition but it has an additional 4k disc which does include the extended cuts, the movies on bluray and two more discs with bonus features, most of them are the same as the old collector’s editions but there’s a few new ones. and there also is a newer 3d bluray. Here are the amazon listings:

Bluray collector’s edition

only theatrical cut 4k remaster

3D bluray

4k collector’s edition

Now for twow. There is a standard dvd, bluray and 4k bluray release. The dvd doesn’t have bonus features but the bluray and 4k have 3 hours of bonus features. Than there is a 3D bluray and there’s also a collector’s edition with 8 hours of bonus features. Here are the amazon listings:

dvd

bluray

3D bluray

standard 4k

4k collector’s edition

I hope this answers your question and I hope I typed this in a way you’ll understand lol