does write up need a hyphen
Yes, "dress-up" does need a hyphen when used as a compound adjective before a noun, as in "dress-up clothes." The hyphen helps clarify that the two words are acting as a single unit modifying the noun. However, if "dress up" is used as a verb or a noun, then the hyphen is not needed.
It does not need to have a hyphen! :)
No. Just looked it up in a printed dictionary. In fact, no work with the 'multi' prefix uses a hyphen. For example, multilateral
No, the word "nineteen" does not need a hyphen when written numerically.
No
It's not a word in the dictionary, so yes, use the hyphen.
You typically need only capitalize after sentence-ending punctuation, which a hyphen is not.
I do not believe that multitasking is supposed to have a hyphen.
No
no
No.