no one knows . at present the best guess is that the universe will keep expanding forever. At some point the density of matter will be so low that stars will no longer form. this is called the heat death of the universe because it will become cold and inert. this is many many billions of years off so dont lose any sleep.

There is no "beyond" the end of the universe, assuming that there is an end to it at all. In Big Bang cosmology, time ends when the universe collapses. Not only does the universe no longer exist, but time no longer exists so there is not "after" the end of the universe.

Science cannot answer that question since no one has actually observed an end to the universe. Scientists can only deal with things that they can see either with their own eyes or indirectly "see" with instruments like telescopes.

This is a subtle and difficult question. Our simple models of the universe, which agree with all observational data now known, have no actual edge or "end" to the universe. Space is either infinite in extent, or it might curve back around onto itself, like the surface of a sphere or perhaps a torus. However, many theories of the origin of the universe postulate a period where there was incredible inflation of space which became our universe.
The universe beyond the region that inflated might be VERY different from our universe, with different laws of nature. Unfortunately, as far as we can tell, we cannot observe this region because there has not been enough time for light to travel to us from this region during the age of the universe.