no
You could consider only tree a noun. Or apple as well, since it is used as a noun adjunct, not technically an adjective. You could also consider "apple tree" to be a compound noun.
No. It is a noun.
because it is an apple tree
an apple tree
Yes you can grow an apple but first you need to grow an apple tree.
An apple seed can grow into an apple tree, which can grow apples
Yes, an apple grows on a tree.
grow an apple tree.
No, an apple grows on a tree.
An apple tree....
An apple tree.
On an apple tree.