I'm simply answering this honestly and I'll confess that I'm not a model citizen on this. In any case, I'm too lazy to think about it. That's the answer. It's why I have a bit of an over the top heuristic. But I also think: surely if one is all powerful, that's not an issue.
> How you can you know 100%? That doesn't make any sense.
God is all powerful, God can devise a scheme in which I'll know it 100%. Here's one for you: I believe that humans have powers that are to quite similar to telepathy, not the same though. We call it WhatsApp. That's extraordinary evidence in such a way that I'll know it 100%. Currently we're moving to machine learning inferring brain patterns. We might actually get to real telepathy.
To me that just sounds insane! But it's true! What?! I am the type of person that finds it quite easy to imagine that I'm simply just a human and nothing more than that. From that baseline our modern world is so crazily magical. It would be awesome if God is in that, but it doesn't need to be in its sheer magicalness.
I have one hypothetical reason why a God (or god-like civilization) might exist. That would be the simulation argument. Also, if we're capable of reproducing consciousness and run simulations, then who is to say that someone isn't already running one? What I do believe is that we might have the potential of becoming Gods as a species. We're trying our damn hardest anyway.
If we're capable of engineering anything and travel anywhere, then one might ask if we can create the exact same universe as we are in right now where (if determinism is real, big if) and if we can do that... Well then again, we might wonder, has this happened before?
So interestingly enough, in my mind, the process of science can turn out to be a very very religious endeavour. Or it might be able to completely dispell it.
It's all speculation during my lifetime though. So I like to keep it to the realms of highly reproduced science (aka engineering and to a big extent physics).
But yea, that doesn't say much about the Christian God, or any religion really. Science is my religion, I simply like the process more of having evidence for things than believing a certain book is the holy word and that I should take it seriously.
I'm sorry if I ranted a bit too much. I don't usually talk about this stuff as it is highly speculative and I have better things to do with my time such as focusing on reality.
I appreciate the non-judgemental tone of the questions by the way.