No, it is not. It would be either most sweet, or sweetest.
They are both somewhat correct, but 'on what date' is the most used one.
correct. but one religon seems to have the most terrorists.
Yes, you can say that in correct English. One of the most cutest is grammatically correct.
In the NBA.
It doesn't look grammatically correct, but not everything that is correct looks that way. When you break the sentence apart, there is nothing missing. It has a subject and a predicate. Although "You are the winner" may be more appealing to most people, I do not believe there is anything grammatically incorrect with your example, as ugly as it may sound. It is correct. You can be be a subject or an object pronoun. subject - You are the winner! object - The winner is you!
Both are correct: "I agree with you" would be used most often, but "I do agree with you" could be used for emphasis.
Under the ground.
"have well and" can be a grammatically correct phrase only if the word "and" is followed by another adverb, with "well and truly" probably being the most common. In fact this phrase is so common that it is best avoided as a cliche.