Inkscape isn't an alternative to Photoshop. Now Illustrator, on the other hand...
a true vector editor is the tool to be using rather a image editor with some vector tools bolted on.nice logos and graphic for web
actually there was cs5.5 and now cs6.PS5 is the latest version, but as a beginner I suggest you to stick with the PhotoShop 8 (CS) because you can learn the basics through that and go for an advanced version.
CS5 is best.