Sanhedrin 47: The Curative Graves of the Sages

If a person ate of the forbidden fats, he needs to bring a sin-offering to atone for it. But if he decides to stop observing the mitzvot between the time of the sin and the sin-offering - and then decides to come back to his observance, he pushed aside the animal and the sin-offering. Can the same animal be used, or once it's been pushed side, is that it? What if the person loses cognitive abilities as an interim instead? (And why does the Gemara need to present both cases?) Also, people would take dirt from Rav's grave as a cure for a fever of one day. Which is difficult, but Shmuel allows it. And a verse suggests that this practice was acceptable, given that it doesn't go as far as acts that were known to be idolatrous. Plus, that which was attached to the ground is not a problem of idolatry. One question is how this relates to other graveyard prayers and traditions.