She said she had better call a doctor. Is it gramatically correct? Is there everything ok with "had better" construction?

please take a look at the sentences down below and tell if they are correct or not Having enough sleep and taking regular breaks are vital. Do I have to use "are" here or maybe "is" is more suitable? Maintaining a schedule and adhering to constant training are beneficial for you. Again, I count things and I'm confused. After plural objects we use "are", don't we??? It's essential not to panic during the exam. Or do I have to say"to not panic"?

can I use a phrase " and so on" in my exam writing? For example, my friends like voleyball, football, tenniss, and so on. Can I use this in an essay for example, or is it too informal?

is there any difference between "off the cuff" and "off the top of my head"?

meet something vs meet vs something?? The new law didn't meet with anyone's approval. The new law didn't meet anyone's approval. My textbook says there should be "with" in that sentence, but I'm not sure. Please, explain it to me

future perfect vs future perfect continious? from my test We _______ (rest) for three weks before we ____(hit) the road again. I think it should be: We will have been resting for three we ( will?) hit the road again. I'm not sure about it. Please give me a hand!!!)

joy or bliss or treatment? what's the difference?? On Friday, we are here for a special _____. Belinda Wilde, our guest of honor, is making her debut at the festival. A) joy B) bliss C) treat D) treatment

let vs allow A well-mannered driver may, for instance, slow down to _____ somebody to cross the road. let or allow? (this is a task from my test and it says the correct answer is "allow". I can't understand why)