will all be dead?

I would hope so although I can't guarantee it as I am limited with experience myself.  I have grown onions and garlic over winter before though and, although I lost a few sets to the wet weather last year, the vast majority were fine.  Having said that it wasn't quite this cold for quite this long!

The snow can actually protect plants like onions and garlic from the hard frosts which do much more damage.
Fruit tree`s can be vunerable in the first winter if the roots haven`t settled in properly. I did fleece the apple tree i put in late last year and it kept the few leaves it had through all the frost and snow.