“Most assuredly, I say to you,
he who believes in me has everlasting life.”
John 6:47

Does this mean that every person who believes in the historical Jesus – has everlasting life? No, even the demons know who Jesus is:

“You believe that there is one God?
You do well, even the demons believe -and tremble!”
James 2:19

Believing that Mohammed founded Islam doesn’t make one Muslim. Being born in a barn doesn’t make you a cow.

The author Merlin Carothers said that one day the Lord spoke to him, “I have no grandchildren.” Carothers was stumped as to what the Lord meant by that, and asked him about it. The Lord told him that no one is saved based on the fact that they grew up in a Christian home. If you think you’re a Christian because your parents were, that would make you not a child of God but a grandchild, and God has no grandchildren. Being born in a Christian home does not make you a Christian, each person must come into the Kingdom of God individually and personally.

“…if you confess with your mouth ‘Lord Jesus’
and believe in your heart
that God has raised him from the dead,
you will be saved.”
Romans 10:9

It’s not to confess with your mouth THAT Jesus is Lord, but to confess with your mouth “Lord Jesus.” Merely acknowledging the historical fact is entirely insufficient for salvation. Salvation is in the confession that you have surrendered yourself and your life to his Lordship.

“That which is born of the flesh is flesh,
and that which is born of the Spirit is spirit.
Do not marvel that I said to you,
‘You MUST be born again.’”
John 3:6-7

More:
Born Again – What Does That Mean