Can I make popcorn with any corn?
The answer it seems is - no, you can't just use any variety of corn. It seems that you need in particular a hard shell around the kernel that is not present in sweetcorn varieties.

I also suspect that it is harder to make than one might imagine, you need a specific percentage of water in the kernel to get it to pop - this is why you can't store unpopped popcorn in the open and once opened needs to be used within a few months, as the water will evaporate and eventually the percentage will become too low to effectively pop.