@wincom -- your comment "for what is mainly said and accepted outside of Scripture...." is problematic.
"many Christians....." what constitutes a 'Christian'. A person can say they are 'Christian' on the basis that they believe in God in contrast to some other entity. Or that a person goes to church on Christmas and Easter. Or that a person goes to a church because it's family tradition / parents / grandparents. They hear a sermon, pay their tithe , maybe get married in the church and are buried by the church. Other than That , the term "Christian" means nothing to them.
So, in That respect -- there probably are and will be Lots of 'christians' in hell.
How many pastors teach Bible these days. How many teach salvation. How many teach the coming reality of heaven or hell / lake of fire and brimstone in every persons' future that Will last Forever.
A real Christian is a born-again believer -- a person who has accepted Jesus Christ as his / her own personal Savior. They are trying to live as Christ-like a life as they can. They are Christ-followers. THAT person will Not already be in hell or on their way.
Everyone has a 'say' in their salvation. They either accept or reject God's gift Of salvation. And it Is true that God already knows -- has Always known who will and who won't accept Him as Savior. We're the one's who Don't know. And we Are told to share the Gospel unto Salvation with all people.
Referring back to your post # 4 -- you're suggesting universal salvation on one hand and on the Other hand -- for children for whom hell was prepared for in the beginning. Your passage in
Matthew 25:41 says the devil and his angels in contrast to your including 'and children'.