Good Day SirIts very common to see rolling friction is less than a sliding frict

Good Day SirIts very common to see rolling friction is less than a sliding friction. My doubt is what makes rolling friction less than sliding (ie the science behind it). When I did some online searching I have seen answers such as its because rolling friction has got less surface area of contact and this makes rolling friction less than sliding. However from what I studied friction is independent of contact surface area and so then how can we say rolling friction is less because of less contact surface area reason. This is my first doubtMy second doubt is when we rub two things together then heat is produced because of friction. So my question is from a molecular perspective why this is heat is produced when there is friction or when we rub two things.My third doubt is how can we prove frictional force is independent of velocity (because in some notes I have read sliding friction is independent of velocity. so my doubt is how can we prove that)RegardsManesh