You should ask God for two kinds of evidence ─ first, a video of [him]self in an easily recognized real situation, and second, new remote information about events on earth that you otherwise couldn't possibly know about. Perhaps you could solve several unsolved murders, locate the bodies of missing victims, and the evidence to convict their killers ─ anyway, something along those lines.
And you should ask God for the means to return and get more such information from [him] whenever you need it.
Not that I know of. But if they did, either the question went unanswered or the person forgot the answer.