Q.Tree Pruning.
Is the Bradford Pear a grafted tree? The initial tree that I planted died from the top down, and another growth came out from the root. It appears strong and healthy, but I wonder if it’s a pear tree. Should I cut out the old dead tree and try to nurture the upstart. It’s about 3 years old.

Yes, it is a grafted tree. The root stock is likely of a pear variety, but unless the grower identifies it, it would be unknown.
I myself left 2 Bradford Pears that died off and left the rootstock. They have served as pollinators for 2 new Pear Trees.