You can save thumbnail preview with image in Save or Save As dialog. Thumbnails in LAYERS palette you can choose thumbnail options from LAYERS panel options (top right corner of LAYERS palette > Panel Options).
No Photoshop CS5 and Photoshop Elements are separate programs.
CS5
yes.
Photoshop CS5
Photoshop CS5
Yes, you can upgrade from Photoshop CS3 (or earlier) to Photoshop CS5 Extended, no problem.
cs5 is better
Adobe Photoshop CS5
In Extended version you have 3D Tools to work with 3D Objects.
Adobe photoshop CS5 (extended)
Adobe Photoshop CS5
Go to C:\Program Files\Adobe\Adobe Photoshop CS5\Scripting in Windows XP or find Photoshop\Scripting folder on your computer for detailed information's.