We use indefinite articles for non-specific singular nouns; for example, "a banana." Is that a banana? I would like a banana for breakfast this morning. I like banana is not correct if you are referring to the non-specific singular noun. If you were given a number of choices for, let's say colors, you could use such a phrase. For example, "which of the colors do you prefer: orange, peach or banana? I like banana." I like bananas is a statement of fact that you like bananas (plural) in general.

Generally the 2nd is correct. "I like banana" would only be used if you mean something like banana flavor, not for actual bananas." Ex: "What's your favorite kind of pie?" "I like banana."

Great question. When you say I like bananas 🍌 you are talking about plural 😊 and in general.

The first sentence is incorrect!

I like banana it means(singular)you like just one banana and I like bananas(plural) it means you like more than one banana.