That puts it in the hardest class of instances for its size (subject to available knowledge), because all instances can be solved by brute force.
The problem is, since the instance is so large, we don't know what happens. No one has ever ran one to completion.
So no, it's not in the hardest class of instances for its size. Its difficulty is unknown.
That puts it in the hardest class of instances for its size (subject to available knowledge), because all instances can be solved by brute force.