A:AnswerYes it will work on all of those devices, and as far as having BestBuy installing it for you, my understanding is that there should not be any cost.
A:AnswerMy web root subscription is through my total tech support which I subscribed through Best Buy. It does auto renew unless you cancel it through Best Buy . You may also be able to cancel through the credit card or financial institution that these automatic drafts are been taken from.
A:AnswerYes, Webroot is compatible with the latest version of MacOS! See this article: https://answers.webroot.com/Webroot/ukp.aspx?pid=12&app=vw&vw=1&login=1&solutionid=3466
-Webroot Community Team