All the subscriptions for a v3 version of Ohanah (started selling at the end of September 2015) have an automatic renewal discount of 20%. You don't need to do anything with it, the system will apply it. 

What if I cancel and then buy again later?

The renewal discount is applied only on automatic renewals.

What if I used a discount on the first purchase?

The renewal discount is not related to the any coupon code that you used. Coupon codes are applied only on the first period.