Yes. A qualification criteria and/or line item selector can be edited after a connected coupon has been delivered. Both can be changed and will be checked for qualification server side at the time of redeeming.
Expiry changes for coupons are dependent upon the method of generation.
Dynamically generated- changes to expiry on step 2 of the coupon campaign will affect coupons being generated moving forward, as the expiry is from time of generation.
Pre-generated- These coupons all already have been assigned expirys so changes will not take effect.