What is the ruling on discarding food that is served at birthday parties and contains pork gelatin, and what is the ruling on discarding a product that is discovered after purchase to contain pork fat?

There is no harm for a Muslim in accepting gifts from non-Muslims on their holidays. Food items should not be discarded merely due to suspicion of containing pork or impurities. However, if it is known or highly probable that it contains something impermissible, such as pork, its fat, or an impurity, then it is permissible to discard it. If you purchase food and then discover it contains pork, and it is possible to utilize it in a way permissible for carrion, then there is no harm. Otherwise, there is no harm in discarding it in the trash.