no
No. The correct is: Hansel doesn't know it happened.
Either is correct depending on the sentence: What happened at the party? What's happened at the party. What's happened to the cookies? What happened to the cookies. ~Note: This is because the word "what's" is a contraction of "what has", so the sentence really means, "What has happened to the cookies?" That's a different tense than past tense, but either can be used.
No, the sentence is incomplete. It needs additional information to be grammatically correct, such as what happened during lunchtime or where it took place. For example, "Today during lunchtime, I met a friend at a café."
"How are you" is a correct sentence.
Yes, this sentence is correct.
No, "too" should be used instead of "to" in this sentence. "All too soon" is the correct phrase, meaning that something happened sooner or more quickly than expected.
You are palpitating. This is a correct sentence.
With the exception of not capitalizing the 'y' at the start of the sentence, it is a correct sentence.
That sentence is grammatically correct.
no it is not a correct sentence.
no_____If the sentence is You do do that (meaning You are in the habit of doing that) the grammar is perfectly correct and the sentence 'does have correct grammar'.
You are missing the subject and what happened. Who fell from the bicycle and what happened as a result.