None of the above (depending on what exactly you mean). The singularity is a zero dimensional point. The surrounding event horizon is spherical, but you can't see it directly - only as a black zone. Why worry about the shape then? I haven't a clue what you mean by that last phrase...a filler theory to complete and uncomplete circle? huh? You mean Hawking radiation. No mystery. Even in space virtual particles are popping in and out of existence all the time in the form of particle-anti-particle pairs, like positron and electron. They quickly recombine and annihilate. But if this happens at the event horizon then one of the pair might be pulled-in and the other escapes. That then can be regarded as a particle being 'emitted' by the black hole because it has supplied the energy to keep the pair of particles apart.There is no theoretical limit. But don't think of it as a beast sucking everything in - common misconception. If the sun turned into a black hole, you wouldn't notice apart from the dark/cold. The earth would carry on orbiting, as would the other planets. A black hole can only attract according to it's mass just like everything else in the universe.An apex is normally a tip or point and a circle has no tip or point. In fact it is sucked-in to the singularity - an infinitely small dot in space. This is where the science ends because we don't know much about the singularity and probably never will, since nothing, including light, can escape, so we have no way to see it or interact with it in any way. Some say it is a tear in spacetime - it could possibly lead to another spacetime - another universe.
