It cost me $800 to have it blown into my attic. It only saved me $100 a month on my heating bill.
Yes, it is fine to do that. You should also put the batts perpendicular to the rafters. This will help tp minmize thermal bridging.
Not a good idea. It really needs to breathe. You can trap moisture and create a mold situation.
Because heat rises, right out the roof.
don't understand the question...