Is there a guide to identify Corn growing, and I have no idea which kind it is?

Not really. All corn plants are very similar at early stages. When young it is even difficult to differentiate from sorghums or Johnson grass. As it progresses some varieties will differ in coloration ie red or purple in the leaves or stalks. A little further on size of the plant will give you a hint if you are familiar with corn varieties. Field corn/ ornamental corn is normally a very large plant. Sweet corn can vary in size from 3 - 8 ft. Same is true of popcorn.

I have ears growing can that help?

Of course at least you know that it is corn. If the stalk is short less than 8 feet, it is probably a sweet corn. When you can open the tip of an ear, the kernals will be very small if popcorn. No way to isolate variety as many have very similar characteristics. Once it is eating size, you can further differentiate by kernal color and taste.

I hope the cost of DNA testing keeps dropping. I saw one offer for $99 for analyzing human DNA:
https://store.23andme.com/en-u...

If it were cheap enough, we could use it to identify plants.