I'm about to buy earpods, but since i have iphone 3g, and i didnt find any info on its compatibility, would like to know if they will work with old iphone? AFAIK every 3.5inch headphones will work
According to Apple's Earpod product page, they aren't compatible with the iPhone 3G at first glance because they aren't listed in the compatible products section.
However, under "Compatibility Information" you should be set:
The remote and mic are supported by all models of iPod, iPhone, and iPad (not all models support volume up/down functions). Audio is supported by all iPod models.
So, while not exactly under compatible products, they should work on your iPhone.