It is not quite clear to me what you have in mind with infinite size + depth limits for your neural net, but once you have sorted that out you should end up with the following game:
Player I plays a program p, and Player II plays a program q.
Player 1 wins iff p halts on input q, and answer Yes if q halts on input q, and No otherwise. Player 2 wins iff ...
As far as I know, sellers can't fully verify that the platform is behaving honestly, so you'll need to trust the platform. A malicious platform could always sell a copy to someone without giving the seller their cut.