hello iPhone 3G owners

can you guys help me out a bit? can someone make a list of iOS 4 features that's not supported for iPhone 3G? i want to add it in the FAQ section. i only know multitasking and screen lock. if anyone can contribute more, i'd appreciate it.

and another thing, is it possible to change the multitask button to single click home button, and 'quit app' to double click?

thanks in advance!