All of the questions asked in this thread are strictly forbidden by the fare rules of every airline I can think of (except probably Southwest). Some airlines (not sure about CO) will impose monetary penalties if they catch you doing this.

Worse, some people have tried to do back-to-back ticketing. This is basically creating two round-trip tickets in an inventive way. For example, buying CLE-EWR-CLE and EWR-CLE-EWR, using both outbound tickets first, and then using the return tickets later or refunding that portion. Another trick is having one round-trip ticket inside of another round-trip ticket.