I have an Iphone 3g spare in the house but realised that it is on IOS 4.2.1 I really need to know whether it can be updated there must be a way. lag wont bother me too much just need ios 5+ without getting an iphone 3gs
No way. To be honest, even if you could upgrade to iOS 5 it would be horrible, not just a bit of lag but prob quite bad. The 3g is basically a modified original iPhone, it is ever so slightly more powerful but not enough to run iOS5. I find my iTouch struggles with iOS 5.