young apple tree, dead at bottom alive at top, is that possible?

[ApplesAndBlue]

tree is approx. 5ft
It has never bore fruit but its an only tree
last two years it has had leaves but this year its branches are still bare, but there are small buds at the top of the branches (these have been there a few weeks though)
I cut into some bark a few weeks ago and it was green so I assumed all was well, however I decided to do the same at the trunk and the bottom half is just showing brown inside (ive not cut all the way though obviously but ive done a decent slit on each side.

is it possible its dead and the top is just yet to turn brown?

im a complete novice at gardening so any help would be great, I have no idea!

Sometimes when small trees and bushes are dying they make every effort to survive by producing growth on the ends of stems and branches. The plant hopes to flower and produces seed to carry on the species.
Having said that, stressed trees can become dormant but still live and come back later. I would continue to feed and water the tree and wait and see.
Do not make any more cuts into the trunk or branches because by doing this you could introduce disease.

Thank you :)