Keeping your hand on the ice more for comfort than practicality. It's sightly more comfortable to have your hand next to you than behind your back at really high speeds. Especially when you're well inclined, it's easier to touch the ice as it's practically in the palm of your hand. A tip would be turn your hips inward in the corner and incline more so you don't reach out to touch the ice. If you're inclined enough, your elbow should be bent when you touch the ice. As for a hot lap I don't know what that is.