1) You can't apply a coupon as an admin to individual members.

2) We use Memberstack to provide live content to subscribers. Sometimes there are technical issues, outages for any reason, or an RMA from members. You could offer them a discount/credit using coupons. Another usage might be as gift certificates.

3) Actual solution is to cancel the actual plan and apply a coupon code on the prompt to renew the subscription at the end of the period. You don't want to instruct paying members to cancel their subscription... :)

4) Allow usage of coupons anytime resulting in members credit or discount from the upcoming payment.