(Mishnah): If Yayin Nesech fell on grapes, he must merely wash them off and they are permitted. If they were cracked, they are prohibited.

There was a case with Baytus ben Zonin who brought dried figs by boat and the barrels of wine broke all over them. The question came before the Chachamim and they permitted it.

The general rule is - whenever a person would derive benefit from the flavor given by the prohibited item, it is prohibited; whenever a person would not derive benefit from the flavor given by the prohibited item, it is permitted; for example, if vinegar (of Yayin Nesech) fell on ground beans. (Since the flavor of the vinegar only worsens the flavor of the beans, it does not prohibit.)

(Gemara): (When the Mishnah differentiates between non-cracked and cracked grapes) it is referring to grapes still attached to their cluster that still have stems; but if they do not have their stems, they are considered to be cracked.

Question: Is the wine that fell on the grapes viewed like prohibited wine falling into permitted wine or prohibited wine falling into a pot of permitted food...?

If it is viewed like wine falling into a pot of food (which worsens the flavor of the food), it is a dispute between R. Meir and the Chachamim as to whether it is permitted. If it is viewed like wine falling into wine, (since it improves the flavor) all agree that it is prohibited.

(R. Yochanan): When the Mishnah discussed vinegar falling into beans as an example of a mixture that worsens the flavor, it was referring to hot beans, but cold beans would be prohibited, as the people of Tzippori would regularly add vinegar to cold beans, which they called Shachlaya.