Couple questions about Christianity

[Double Down]

Hi. Non Christian here wondering if someone could answer a couple questions for me.

1. Before Jesus, were all people sent to Heaven? Or were they all sent to Hell?
If they were all sent to Heaven, then why would God send Jesus down? Why create this opportunity for people to go to Hell? Also, if they were all sent to Heaven, then who if not humans were in Hell before Jesus?

2. I was always told by my Christian friends that those who did not have an opportunity to find out about Christianity and therefore can't accept Jesus (such as indigenous peoples in remote areas) are given the benefit of the doubt and get to go to heaven. If this is the case, then how do missionaries justify doing what they do?