For the following people, please specify if you think they are saved or not and what leads you to think so. Also please indicate if you believe in single or double predestination or not.
1. A miscarried baby
2. A 5 year old who dies before becoming a Christian
3. A 15 year old who dies before becoming a Christian
4. A Christian who develops Alzheimer's or other dementia, rejects that they were ever a believer and passes away
5. A Christian who injures their brain, suffers permanent amnesia, forgets they were ever a Christian, dying many years later having never remembered
6. A person with split personality where one personality identifies as Christian and the other rejects Christianity
7. A Christian who drinks too much one day, while drunk rejects their faith and is killed in an accident before they can remember and repent
1. Definitely, still innocent, they could not have possibly sinned then
2. Possibly still innocent, it can depend on individual development. A lot of 5 year olds won't really know what Jesus' sacrifice means beyond just regurgitating what they're told, likewise, they won't fully understand the concept of sin either. As Paul said, "alive without the law once". It's also possible that they did know right from wrong clearly and did wrong consciously.
3. Probably not, they understand right from wrong, have done wrong (that's that Romans 3:23 there, you're not going to have someone who never does wrong). They could have some sort of developmental disability that might change that.
4. Yes, they've developed an end of life stage degenerative disease, that's biology, that's the flesh dying, if they're saved, their spirit probably feels trapped.
5. Yes, their flesh forgot, their spirit does not, but if they don't remember how to live in the spirit and only know the flesh, they're going to walk in the flesh, I'd think someone would remind them and teach them the gospel again though.
6. Depends heavily on the nature of their mental illness, is it a biological cause, a chemical imbalance, they can possibly still be saved, maybe they're being chastened for disobedience, or.. if they were never truly saved, demonically possessed.
7. It sounds like a 1 Corinthians 5:5 situation, destroying the sinful flesh so that his spirit might be saved in the day of the Lord Jesus. So.. possibly he was saved and just walking in the flesh.