Are you trying to test two different home pages of your site which are completely different ?.
One of the most common ways A/B testing is utilized is to test two different design directions against one another. For example, the current version of a company's home page might have in-text calls to action, while the new version might eliminate most text, but include a new top bar advertising the latest product. Experiences inside A/B test ( Experience A, Experience B) are basically different versions of a same page.
By Can I choose different links as A/B test? - Do you mean to Add additional pages or sections to the activity. If yes, click the Configure gear icon, then select URL. Enter the URL in the Activity URL field.