The other possibility is that there is no function. That the sequence is what it looks like, defective. Many say that the presence of the b-hemoglobin Pseudogene is very strong evidence for a common ancestor. I see evidence for the existence of either viral or enzymatic activity that creates mutations. So I think there is a mechanistic process that has produced many of the Pseudogenes that we have, rather than a random process.
Viruses have enzymes that, under the same conditions, do repeatable reactions.
I think so. If both chimp and human DNA have the same active sites, I would expect the viral proteins to react in the same exact way to both human and chimp. Common descent or common Ancestor is not the only answer.