Will try to answer the questions.:

1. We can't, although if we observe very carefully how the universe work we can find some glitches and to manage to start guessing on what actual machine the sim is run :P

2. Existence is universal. Even the most 'physical' implementation boils down to 'bits'. It is all structured matter or formed substance to a degree that they are totally inextricable - nobody up to now have been able to point out an example of formless matter or immaterial structure. So virtual is as real as any real. VR code is homoousic / isosubstantial with physical laws, not occasionally few years ago TCP/IP have been dug out of one of the String theories of physics.

3. If it is exact copy of yourself it is yourself. Quantum no-cloning theorem. Because location is part of specs of yourself - it is TRUE yourself if everything is the same up to the horizon ...