Welcome to the forums.
Please create new posts for your other unrelated questions. Grouping unrelated questions into one post will create a confusing thread.
Additionally, please remember that proper English requires capital letters at the beginning of a sentence and that the pronoun "I" is always capitalized.
I will answer your first question.
You say "a dozen" or "dozens" but not "dozen." The same with "score" which means 20. He gave her ... a dozen flowers.
I would ask further posters NOT answer the other questions here and wait for the new threads so this doesn't become a tangle of crossing posts on different themes.
Student or Learner