What is the most populated/numerous stellar system in which the orbits of all objects are known?
What is the most populated/numerous stellar system in which the orbits of all objects are known?

The answer is none. Other than our own solar system, astronomers don't know if they know all of the large bodies (aka planets) orbiting any given star system. Presumably other star systems have asteroids, comets, and other stuff. The orbits of those small bodies in star systems is unknown, and will remain unknowable for a long time.

We don't even know that for our own solar system. If we did, we wouldn't have to worry about killer asteroids and comets.