What is the difference between photoshop CS and CS3? ?

i can’t afford the CS3 because i’m still a student and my parents wouldn’t buy it for me.
i would just like to know what is the difference, and if photoshop CS has brushes like in CS3? or is it just the basic cropping, filtering, deleting objects? PLEASE ANSWER! thankyou..

How To Give Abstract Brushes That Glow Effect But On A Photo Using Photoshop CS4?

Like The White Abstract Brush Used In This Photo:
I wanna Know How To Get This Effect On A Regular Photo, I Have Seen Tutorials, But The Use Gradients Instead & When I Try The Same Thing On A Photo, It Doesnt Come Out The Same.

I can’t change the shape of the brush cursor on PhotoShop 7?

You know when we use different-shaped brushes, the cursor would reshaped into what the brush is like? Well, my cursor constantly is in ‘plus’ shape, like
_ _
(ignore the -)
And it makes me uncomfortable when I want to draw in PS7