My understanding is the single layer BD was used for the 3D version / presentation, though I don't have that edition to confirm.
For the 2D, the main feature and video extras are on a dual layer BD.
"Sandra's Surprise," if it is what I think it is, got incorporated into the "Sandra and George" featurette.
The scoreless version apparently didn't make the cut for this release. Yet another reason to think there's going to be an "extra weighty edition" down the road.
<strong class='bbc'>Gravity Blu-ray Review</strong><p>Alfonso Cuarón’s zero-gravity masterpiece thrilled viewers in theaters thanks, in part, to 3D and Dolby Atmos technologies, but how does the film hold up in the home viewing environment where 3D displays and 7.1 surround setups aren’t...