What is the ruling on placing the hand on the chest by placing the forearm on the forearm and grasping the elbow with the palm in prayer, and is there any evidence for this? Is this a madhhab of any of the imams? And what is the correct position of the feet during prostration, and is it better to keep them together or spread them apart? And what is meant by the "sole of the foot"?

We have not come across the described manner from any of the scholars. The correct way to place the hands in prayer is to put the right hand on the elbow of the left hand or close to it. As for the correct position of the feet during prostration, it is to prostrate on their tips while facing the Qibla (definition) with them. Some scholars have recommended separating the feet by a hand span.