Is this a strictly hypothetical thought experment-type of design? Ie, nothing that could be realistically built and tested? I am asking because our current understanding of physicas is that it is practically impossible to know exactlt the state of even a single particle, let alone of the whole universe, to the precision even theoretically required to "determine" the next state. (Outside of simplistic esperiments in a laboratory.)

This is not a limitation of technical prowess, this is a quality of quantum particles, of thermodynamics, etc.

My point is, if it is impossible to construct such an experiment, it means it is not a question within the domain of science. Science deals with hypothesis which can be realistically disproven.