My husband & I have an XBox One S & have a friend with an Xbox 360. We want to play Borderlands. Is that possible?
If I understand your question correctly, you wish to play Borderlands on your Xbox One, by borrowing it from a friend who only has an Xbox 360.
If that is the case - yes, you can play it. There is a set list of games that the Xbox One is compatible with from the Xbox 360, and Borderlands 1, and 2 are on that list.
However, if you are talking about the reverse, or even cross-platform play: no, that is unfortunately not possible.