Well no we didnt see him do that. he ran out of Naural Chakara and lost Sage mode, which is how he almost lost till Hinata came to try and help and almost got killed herself which was where Naruto went in Beast mode and went mad, only to get sucked into the the Gods path's jutsu wich was where he got the time to get enough Natural Chakara for Sage aging... but if it was to truely mix then i think it'd be beast BUT he cant mix it cause there wont be a way to balance that out with the Kyuubi's chakara.. well so far anywaysWe don't know, we saw him mix them before(when facing nagato) but he didn't do anything. I'm guessing it will make him stronger, faster, increase his durability.(just increase all his attributes)
You guys, those one word answers are considered a spam