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#30
Since you are dual booting both 32 bit & 64 bit versions of Window 7 you can use the "other download options" just below the download button to download either the 32 or 64 bit versions of IE 10 RP.
to answer your 2nd question yes IE 9 will be removed and upgraded to IE 10 but can be restored again through - Control Panel > Program & Features > View installed updates then uninstalling the "Windows Internet Explorer 10" update, the spelling package and other updates will also be removed automatically upon restart.