Hey,
For that function you need to register at YouTube and verify the mail address and also address with your mobile phone (in Germany is it to get access over the 15 min posts). How big they could be then I can't say but if bigger your upload will take more time

more than 256kbts for audio will not be stored there I mean you can upload higher but it will recompile your stuff to save place on HDD and also when watching

But all info also Availabe at the help page of google. I used the search function

Regards
Christian