God is all powerful. If he can cause a virgin birth and produce the Son of God out of it, is it impossible for him to do those things you speak of above? Consider this passage, " And it came to pass, that, when Elisabeth heard the salutation of Mary, the babe leaped in her womb; and Elisabeth was filled with the Holy Ghost" (Luke 1:41)
Apparently John The Baptist was able to recognize the sound of his savior's mothers voice when he was yet unborn, or else why would he leap in the womb? God is sovereign and is not bound by the limitations understood by man.
Many conditional time Salvationist Primitives will often use the same question you posed to me to others, to convert them to their doctrine. I know through firsthand experience. (I love them and learned much from them regarding how eternal salvation is wrought, but am afraid they are misguided when it comes to time salvation).
Now as to the question of will all the elect hear the gospel scripture tells us," being confident of this very thing, that he which hath begun a good work in you will perform it until the day of Jesus Christ:", would it be considered performed if the end result was a "regenerated" Muslim who dies not knowing his savior? Also, this verse touches on time salvation by showing it is God who performs the works in us. Scripture teaches us anything good that comes from us, is from God because nothing good is in us outside of God.
I would have perferred a detailed explaination....replete with scripture detailing how those who don't physically hear...can hear as you appear to suggest. See this is now all a "what if" synerio (sic)....one that leads to continued speculation.