Yes, you do. "Stay-at-home" is hyphenated, but "mother" does not have to be. Either version is grammatically correct.
No, it is never hypenated
no
stayathome
Most people would spell it sixteen-year-old child. But over the last 20 years, people are ignoring the hyphens.
Hyphens are used to link words together to form compound words, such as "well-being" or "mother-in-law." They can also be used to separate syllables in words that are broken at the end of a line in writing. Additionally, hyphens are used in some prefixes, suffixes, and to avoid ambiguity or confusion in writing.
Two thousand nine hundred sixty-six. You only use hyphens for numbers between 21 and 99.
Hyphens not needed
M-i-s-s-i-s-s-i-p-p-i (without the hyphens of course). Be sure to always capitalize the "m".
There are no hyphens in the word ago.
You use hyphens to make compound words that are not recognizable in common usage.
It changes the hyphens into end dashes.
No. The phrase is spelled "by the way" (an aside). You would only use the hyphens if the phrase "by the way" was being used as an adjective, as is seen in the term "out-of-the-way location."