If we're a simulation of a parent universe that is exactly like us just of it's past or an alternate past, then we likely should be able to achieve simulating our own universe within ourselves. Otherwise we're not actually a simulation.
There's another line of counter argument that various results in QM and computing theory would suggest that it's mathematically impossible for the universe to be simulated on a computer (i.e. the parent universe would have to look very different from ours vs ours in the future). But I don't recall the arxiv paper.
Of course it is. Scientifically the simulation “hypothesis” is actually the simulation idea and isn’t scientifically valid yet seems to be treated as such for some reason.
Where have you seen this?