The Hyphen and the Dash

Does a compound word come before or after a noun?

Is this an incorrect or correct use of a hyphen? The lead singer was well-known.

Is this the correct definition of a hyphen? It is a shorter mark that is often used to link two or more words together.

Is this a correct use of a compound modifier? The bottle was a lightweight-green plastic.

Is this the correct use of a prefix? My grandparents were born post-World War Two.

True or false? This number needs a hyphen: 3,782.

Is this the correct definition of a dash? The longer line used as punctuation in sentences, coming in between words.

Is this a correct definition of a dash? It is not used for emphasis.

True or false. The M dash is short than the N dash.

Is this a correct use of a dash? The woman thought she was going to pass -- but I saw her test -- and she had failed.