(1)
Allotropism is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of these elements.
Carbon can exist many forms in the nature one of these fonts is diamond. It means carbon atom get arranged in a definite sequence to form diamond.
other allotropes of carbon are graphiteandbuckminsterfullerene
(2)
True Solution is a homogeneous mixture of two or more substances in which substance dissolved (solute) in solvent.
Particles of true solution cannot be filtered through filter paper and are not visible to naked eye.
One example of true solution is salt water solutions , which is a mixture of water and salt. You can see the salt and water will stay a solution.