Both "fenced-in" and "fenced in" seem to be correct, so it is up to you to decide which one looks better in your particular writing situation. Personally, I would use the hyphenated version.
It is not hyphenated.
Motorcycle is not hyphenated
No it's not hyphenated.
words are only hyphenated when they have a separate meaning when separated than they do when hyphenated
It can be. Some words can be seen both hyphenated and non-hyphenated.
Yes it should be hyphenated.
No, "hardworking" is not hyphenated.
No. Well above is not hyphenated.
peace of mind is not hyphenated.
No, "homework" shouldn't be hyphenated.
Yes it should be hyphenated.
No they shouldn't be hyphenated.