At the end of the fourth level, you gotta defeat Neo Cortex. Can anybody tell me how the hell you do it? I dont see the point in the level, just seem to jump around and die, someone help please, how do i win the level? lol.

You mean fourth boss, not fourth level. Anyhow you want to jump on the platforms with the gems. Cortex will try to shoot you, but you want to get off the platform and have him shoot the gem instead. When he shoots a gem, he loses 1 health point, so you defeat him when you make him shoot all 3 gems.