there is a recipe on tastybrew.com with whole kernel canned corn. i have been thinking of using frozen corn in similar fashion for a CAP i am planning.
I think I'd be really skeptical of most of the recipes there.
I'd be really skeptical of any recipe with canned corn. My gut reaction is "WTF are you thinking?" But I see the OP isn't contemplating this route, so I'll calm down.
You can use any form of corn; I've used flaked maize and grits/polenta (basically the same thing; I avoid instant-anything).
Whole dry corn could tear up your grain mill; a Corona mill is better for this, as is the mill attachment on a kitchen-aid mixer. You're more grinding it than milling it like malt.
Yes, you need to gelatinize the starch, which only happens at hotter temps (above mash temp). A cereal mash involves adding some pale malt in with the grits. This explanation isn't bad: http://www.winning-homebrew.com/cereal-mash.html
If you use flaked maize or quick grits, you can throw them right in the mash. They're pre-gelatinized. The flavor won't be as good, though. But it might be good enough.