Yes, with a higher success rate of becoming a SPARTAN-III than a SPARTAN-II.
Yes, but the augmentations are less drastic than the augmentations on the SPARTAN IIs. The reason behind that being that they needed a large supply of augmented soldiers (the SPARTAN II augmentations often resulted disfigurement or death) and the SPARTAN IIIs were easier/cheaper to produce. This resulted in a large number of troops that were much better than average, but not as good as the IIs. The IIIs were often sent on suicide missions that regular squads of troops couldn't pull off. They chose to go with quantity over quality for the IIIs.