You can start subscribing through game cards and automatically pick up the rewards based on how many days you decide to subscribe, you won't lose the 30 days free but I guess in a way they do become kind of pointless.

It is a one time reward. There are rewards for ever 30 days. If you subscribe for the first 30 days, you'll get the Wind-up Cursor Minion and Fantasia. If you decide you want to disappear and come back later and subscribe for another 30 days, you will get the 60 days reward (it's cumulative).

The last one, we'll have to wait and see. They have made no announcement as to what they plan to sell in the future.