100% cfd right now.
There is no such thing, unless you are rounding. CFD cannot reach 100%, it can only approach it.
I think with the right conditions a rare occurrence similar to finding a 50BTC hash reward using CPU mining solo could occur to make 100% possible; in fact, I think the odds are considerably higher ;D
No, this is impossible :)
There is always a small chance that NO suitable hash exists for given combination of transactions and other data.
That's why you can't calculate required time for 100%