In Extended version you have 3D Tools to work with 3D Objects.
Yes, you can upgrade from Photoshop CS3 (or earlier) to Photoshop CS5 Extended, no problem.
yes.
Adobe photoshop CS5 (extended)
Yes. See the Related Links below, it looks like it's $349
No Photoshop CS5 and Photoshop Elements are separate programs.
CS5
Photoshop CS5
Photoshop CS5
cs5 is better
Adobe Photoshop CS5
it all depends on the amount of discount you have and what version you are looking to buy. The most expensive being photoshop cs5 extended which costs something like $999
Yes, if you're a qualified student or teacher - Adobe will give it to you for 80% off the normal price