Insulating Crawl Space (formerly garage)

Converting garage into family room. Framer starts today, so I can move past the framing questions, and onto insulation. I asked an insulation question before, but my design changed today, so asking for new advice.
I will now have a 3 foot crawl space (foundation walls and existing garage slab), then a full sub-floor with insulation (2x10 R30), and then 9' of stud walls.
Questions about insulating the crawl space:
(1) Do I still need to put foam board insulation on the foundation walls, now that all of the foundation wall will be below the floor? Or will the floor R30 be enough to keep out any cold coming from the foundation walls?
(2) I still want to put a 6mil poly vapor retarder down. Should the poly now cover all the foundation walls, as well as the slab?
(3) How should I physically attach the poly to the slab/walls? Does it need to be stapled, glued down, etc?
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