Can someone please help me with these grammar issues I am having??

First issue is, what's the deal with cannot?

Why don't "donnot" "willnot" etc exist? Why just cannot?

also is it still proper to space them apart like: "I can not go"???

My next issue is does can't, don't etc. really equal do not and cannot??

Like, are they completely interchangeable?

When my teacher asks me "Didn't you do your homework?"

Does that mean "Did not you do your homework?"? Sounds weird.

Doest that make sense??

Another example:

"Why can't I play" = "Why can not I play?"??

I know it probably makes me sound dumb but can anyone help explain?

Tradition, custom.
No. See above.
The meaning is the same, but the usage is different. See above.

Why can't I go?
-Why can I not go?

Didn't you do your homework?
-Did you not do your homework?

'Cannot' is one word. Can and not are not supposed to be separated.

Nah. English is a bitch of a language to learn (if it's not your native language) from what I hear.

"do not" and "will not" exist.

Yes - can & not are normally two separate words.

don't = do not, won't = will not (very old)

But correct English.

Oops - I read it as Did you not do your... Mea culpa.

"Cannot" as a single word is just one of the many idiosyncracies of our writing system. It's an exception. None of the other auxiliary verbs ("helping verbs") can be combined like that. As I've often said, I think the people who make these decisions do it just to confuse foreigners.No, that is considered improper--in almost all cases. The exception would be when you're writing dialog and the speaker is speaking that way for emphasis. "Johnny, you can NOT wash a cat in the dishwasher. Don't even think about it!"Yes. The difference is not in their literal meaning. The contractions are considered somewhat colloquial and are frowned upon in all but the most informal writing, such as here. But to speak them as two words is considered somewhat formal, at least in America. Data the android on "Star Trek" was programmed to be unable to speak contractions, and his speech sounded very stilted.Well, yes, in the sense that no one will ever misunderstand you. But if you use contractions in writing they'll think you're not well educated, and if you don't use them in speech they'll think you're a foreigner. That's because that's not how we say it. It's "Did you not do your homework?" You just have to learn that and make peace with it. It's not logical.Contractions have their own grammatical rules. It is incorrect to say or write it that way. You have to say, "Why can I not play?" I'm sure you sense this instinctively when you speak in the first person singular, because there is no contraction for "am not." You have to say, "Am I not invited to your party?", not "Am not I invited..."You don't sound dumb. You just sound like someone who is learning English as a second language and you wonder about all the weird stuff that we take for granted. There's a thread on that topic right here in Linguistics. It kind of depends on what your native language is. I'd be surprised if most people don't find French even harder, so long as they don't speak one of the related Romance languages. It has most if not all of the same problems as English, only worse. Phonetics, grammar, idioms, writing system. In addition, the pronunciation of a word can change based on the word that follows it, making it difficult to understand speech.