How can I make iOS 4.3 apps go onto my iPod 2G? Last Christmas I was given an iPod 2G and it runs on iOS 4.2.1 and I have found it very hard to find apps that go onto my iPod, is there anyway I can make apps that run on iOS 4.3 an above go onto my iPod?
No. Unfortunately, due to hardware limitations, Apple has limited how far you can upgrade iOS on particular devices.

See this question for a similar situation. Perhaps this Q/A would explain things better as well.