This is for the original Odessey: https://en.wikipedia.org/wiki/Magnavox_Odyssey

This is the closest thing to a "romcart" you can get for the system.

Will this work with the Rifle games?

Yes, this was one of Boojakascha's original purposes for making it, I don't have the Rifle for the odyssey myself to test it with, but it should work as intended.

What games does it play?

You should be able to play all the original game card variants for the original Magnavox Odyssey system, and many of the homebrew that has been produced since. Note that some homebrew have custom hardware and one or two have custom game cards; these will NOT likely to be replicated with this multicard. The switches may also help to produce unique effects, but I don't think this has been documented yet.