According to the sources I've found on a quick search, you should hyphenate 'coauthor', i.e., it would better be: "co-author".
no.
You do not hyphenate the number.
Generally co-author should be hyphenated, but the relaxed rules of modern times often present coauthor as one word
responsible
??
Dave and Larry wrote a book together, Dave is the main author and Larry is the coauthor.
coauthor
no.
Don't hyphenate; ongoing is one word.
You do not hyphenate the number.
I think it's more accepted to hyphenate it.
You hyphenate it only at the hyphen.
You do not need to hyphenate.
The word coauthor is a noun. The plural noun is coauthors.
Generally co-author should be hyphenated, but the relaxed rules of modern times often present coauthor as one word
You would hyphenate "thank you" when it is used as an adjective before a noun, such as in "a thank-you card."
Can you, or should you? You can hyphenate it if you're moving between lines in a paragraph and need to break up the word. You shouldn't hyphenate it normally.