Cooper's bones were frozen ostensibly to prepare it for slicing with a laser microtome. According to the Wikipedia entry for "laser microtome", "In contrast to mechanically working microtomes, the laser microtome does not require sample preparation techniques such as freezing, dehydration or embedding. It has the ability to slice tissue in its native state."
It doesn't make a lot of sense that Arastoo wouldn't be at Sweet's funeral considering that he not only knew and worked with Sweets, but that he is also Cam's boyfriend and would be there with her.