Layers of the Earth

B - Basic, I - Intermediate, A - Advanced

What is the difference between a layer based on composition vs. response to stress? B
In the context of rocks, what does "stress" refer to? [What is the meaning of the word context?] I
Which layer is a subset of the other - crust or lithosphere? B
Which layer makes up a "lithospheric plate" - crust or lithosphere? B
How does the composition of rock change across the lithosphere/asthenosphere boundary? B
Is the mantle molten? B
Does lava that appears at the Earth's surface originate in the molten outer core? I
How long have the Earth's layers existed? A
Was the interior of the early Earth more or less homogenous than it is today? A

Other references may refer to the layers recognized on the basis of response to stress as "mechanical layers."