There is a brief flashback (32:00) to a difficult child exorcism. He is begging for help, and we know whatever happened was very hard on his body and spirit, and resulted in death. However, I don't remember seeing anyone or anything directly harm the child.
32 mins in, Priest discusses an exorcism gone wrong that led to a child's death. We see a flashback of the child weakened, but not the death. Later, the demonic presence takes the form of the child to taunt him. The form isn't gory or anything; just pale.
47 mins in, the suicide of a 12 year old is mentioned, but nothing is shown or further discussed, and it is assumed to be related to the presence.
In the most technical sense, yes. At the climax of the movie a religious relic is broken open to access its contents. No one is shown mourning its loss.
Ignore the previous comment. You see it multiple times throughout. I got my boyfriend to skip over it at the beginning but at 28 minutes in, it's been shown 3 times already