Your selected question
If I book a coachcard online now, then book travel for tomorrow, am I eligible for the discounted fare immediately, even if I haven't yet received the card?
Not if you are travelling tomorrow. When you purchase a ticket with a coachcard discount, you need to be able to show the driver your coachcard when travelling. If you do not have your coachcard when travelling, the driver will ask you to pay the full adult fare.
If you book a coachcard now, you can still book future travel using the coachcard number you have received, but you must make sure you have allowed enough time to receive the actual card before travelling.