Does iPhone have a secondary camera?
well, not the current version. the new iphone 4g (which will arive sometime near september) will have a front and back camera. the current version has a back camera. the new version will have an added front camera for video calling. it will also have a secondary mic for clarity.
This depends on the interpretation of the question. iPhone 3G has a camera that is capable of taking both video and still image, but Apple has limit the iPhone 3G camera to only taking still image. It is possible to take video on the iPhone 3G using Cycorder, but doing so require you to jailbreak your iPhone 3G.
iPhone 2G, iPhone 3G, and iPhone 3GS all have camera that is capable of recording video, however, Apple impose limits on the iPhone 2G and iPhone 3G that disallow video recording, in order to promote the more expensive iPhone 3GS. To record video on iPhone 2G or iPhone 3G, one must jailbreak one's iPhone and install Cycorder, which is available for free.