1. Until you tell us what carrier and what "X-place" is, you won't get a definitive answer. No reason to play NSA here. The facts are important.

2. The general rule is that if you no show for a segment the remainder of the ticket is cancelled and retains whatever value the fare rules provide. If you have found a great deal, it is likely that it is a non-refundable ticket. In that case, your ticket will be cancelled and you may find that you have anywhere from $0 to a credit for the ticket less a fee, typically between $300-500.

3. On the return, you may be able to skip the final segment because you don't care about the ticket being cancelled, but you won't receive any mileage for it and that is presumably one of the goals here.

Again, provide some facts and you will get pin-point accuracy answers.