If your at the outter edge of space, what is on the other side?

The geometry of the universe is non-euclidian. if you carry on going in a straight line you will eventually come back to your starting point.

You are assuming there is some sort of edge. That is an incorrect assumption. Even if the universe is finite (which it is probably not), there wouldn't be an edge. Think of the surface of the earth. There is no edge, but it is finite. With curved space-time, the same thing can happen.

there are three theories; one is, well your question. The other, like the world for example, if you walk in a completely straight line, theoretically you would come back to same spot. The last one is that it goes forever.

There is no outer edge.

Anything that would be beyond the edge, belongs to the universe!