flashlite

What's the difference between each version of flex?

According to this page there's flex 1,2,3,4,what's the main difference between them? Is there a version of flex that supports flash lite 2 which my project is using? ...

Has any one used Flex 1.5 for mobile apps?

I know its now Flash builder 4 and it is grate. But FP for mobile on Nokia is still quite not up to AS3... while my audience has mostly has quite old Nokia phones... That support like most of FP7-8... Has any one experience of using Flex 1.5 for creating mobile apps? Is my idea ok or there are some really big problems on my way? Mainly...