A:AnswerAt the end of the 15 months you have an option to renew the subscription for 69.95 or choose another option for shorter amount of time. If you do not renew with any of the options your access to the programs is limited.
A:AnswerI would check in with BestBuy first to ask the process of how to switch to a family plan - especially if they set up your individual plan . Their support team should let you know you next steps or if you need to reach out to Microsoft directly.