A - Yes, you will get the rewards. If you buy 120 days, you'll get the 30, 60, 90 and (if they exist yet) 120 day rewards, all at once when your payment is processed.

B - You can buy crysta to add to your account. You can do this either with PayPal, or buy getting an Ultimate Game Card.

C - The collector's edition items, and the veteran reward items are NOT trade-able.