Islam is a lot less theologically complex than your questions seem to indicate. The whole idea comes from a single line of text in the Koran, and there is no elaboration on the idea after that.
Islamic “scholars” have of course taken it upon themselves to expound on the idea, but mostly they seem to simply debate the exact number of virgins that will be provided, as there is some controversy on that point due to possible copying errors.
The whole idea comes from a single line of text in the Koran
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No, several places.
http://wikiislam.net/wiki/72_Virgins#Selected_Quotations