It’s not really a guessing game, it’s a there’s his gospel, we follow his gospel and we’re rewarded, which he will ensure everyone has an opportunity to, or they can choose otherwise and receive the level of reward they so desire. No one’s going to force somebody to live in a specific way; That’s against the point.
And God is good because he gives us a choice. Choice means we can become our own individuals, make our own mistakes, learn, and grow. Which to us is the fundamental answer to the purpose of this life. (Buddhism “Life is Suffering”) Otherwise, what’s the point of it all? We’d be hollow machines, always living in a good but un-understanding state of being with no opportunities to grow and move forward.
It’s the assumption / pretense that there’s a single right. And that, you can ask of God to find out. It’s also under the assumption that again God is a God of mercy and won’t judge you for what you didn’t know. Cause if he’s a perfect being, there must also be a perfect fairness in all he does as well.
Though it’s a very genuine concern / question to have for sure!