Don't make this tough.
There are two forms of unbelief. One is from not hearing or not hearing enough of the correct doctrine, the other is rejection of what one has heard.
Rom 10:9 That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved
If you have never heard this in any way shape or form then you cannot possibly believe it.
Rom 10:14 How then shall they call on him in whom they have not believed? and how shall they believe in him of whom they have not heard? and how shall they hear without a preacher?
But if you do believe it then you 'shalt be saved'.
And if you've never heard about speaking in tongues or prophesy as a part of God's will:
1Cr 14:5 I would that ye all spake with tongues, but rather that ye prophesied: for greater [is] he that prophesieth than he that speaketh with tongues, except he interpret, that the church may receive edifying.
You will never know about it. If you don't know about it, how can you believe it?
Act 19:1-9 Talks about Paul following Apollos through Ephesis. Apollos taught what he knew and that was the equivalent of Romans 10:9,10. He didn't teach about the baptism of holy spirit. Paul found out about that and took those saved souls a step further.
Act 19:2 He said unto them, Have ye received the Holy Ghost since ye believed? And they said unto him, We have not so much as heard whether there be any Holy Ghost.
Clearly there are those who have never heard enough to get saved. They do not believe and they are not saved. Their unbelief is from not having heard.
Clearly there are those who have have heard and still do not believe. They are still unsaved and their unbelief is a matter of their free will decision to reject Christ.
There are those who have heard, and have believed enough to be saved. But if they have not heard about matters of the spirit, how will they know about them? Clearly they are saved but do not have further belief because they are ignorant.
And there are those who are saved and who have had the opportunity to hear more of God's word. Clearly they can only believe what they are exposed to. And then it is a matter of choice on their part. If they are taught about walking in the spirit instead of in the flesh and they reject those teachings, then they do not believe God's word at that point.
How many people say that they believe in salvation by grace not of works, but still work for salvations? They clearly do not truly believe that savation is a free gift and are trying to earn it.
But none of that means anything when you look to the Early Church.
The people at Pentacost heard NOTHING of the Holy Spirit Baptism that was to occur, yet they spoke in tongues, had the gifts of miracles, all of it, and NOT ONE had heard of any of it and it had NOTHING to do with spiritual maturity, and NONE of them tarried for that spirit after Salvation.
Today's modern Charismatic movement is so far removed from the Biblical example it is almost cult like.