it receives close to 20Hrs of sun per day (as sun never sets here up in north)

Because it does have some shoots, likely the portion above them is dead.

I just checked, more than half of the tree is dead. Should i cut it out ?

I still cant understand how this happened to both my trees :(

Zone 2 is pretty cold! Perhaps the cold killed everything above the rootstock.

as you can see, I have tulips for Zone 3a there. Cherry survived last winter, Also we only had couple of days below -40 last winter. these plants will survive -45s.

Thanks Lucky. I will go to the garden center and ask them whether they can replace it. It came with a lifetime warranty. I wonder whether they will replace it as it is still alive. between all the shoots are coming from above the graft. if it couldn't survive the last winter which was mild, i dont think its going to survive a typical arctic winter.