Yes it is correct to say "Have a wonderful Holiday."
Yes it is.
You should say for your convenience it is *gramatically correct-*just means correct
Yes.
Yes, there is a verb and and a noun and they are in the same tense therefore it is gramatically correct.
That's not even a complete sentence. The words TO, SAT, THIS, PEOPLE and IS can not be combined in any way to make a grammatically correct sentence. ------------------------------------------------------------------------------------------------------------- Assuming the question should be Is it gramatically correct to say, "This people is..."? then it is not correct. One should say, "These people are...".
I don't see why not although beginning a sentence with 'or' is unusual.
No. It would be better to just say those or these.
Yes. "She has no idea that you are even here." is a correctly formed, gramatically correct sentence.
No. You would normally say something like higher up.
No. I would say: "You and her will begin to ship the product".
no. the correct way to say it is "what wonderful weather."
It is correct