RE: domain registration add-on
Actually Add-On is always added to a sold plan and its billing cycle will be dependant on that sold plan. Let me explain you with example how billing cycle works for add-ons:
If my plan has billing cycle of 6 months and I have added a domain registration add-on of worth 2$ to it. In case of Bill with Plan, customer will be charged $2 after every 6 months. In case of Monthly Biling, customer will be charged 2*6 = $12 after every 6 months for this add-on.
HC Support Team