Does the universe have a top and bottom? If so, would it be resting on something or is it free falling?
We can only theorise about what is beyond the universe, as it is obviously impossible to measure anything about that currently.
Firstly, the universe is likely spherical, so has not only an expanding top and bottom, but is expanding in all directions at once. Think of it as a bubble - inside of which is everything - which is expanding.
Secondly, even if we were able to reach the edge of the universe, we would likely not be able to measure anything beyond it - we don't even know if there is anything beyond it.
Thirdly, the edge of the universe is an uncomprehendingly large distance from us, therefore it is nigh on impossible to even measure or record any signal from the edge of the universe, let alone go there.