If a human ingests a mouse's feces, the human might be exposed to rodent-borne pathogens. The person should be tested for Lyme disease, typhus, and salmonella.
You should be okay, unless the mice has consumed something you are allergic to/toxic. If you feel sick, see your doctor.
You digest it and void it.
For the same reason human feces does - Rats are omnivores. If a human and a ratty both ate lasagna for three days straight their feces would smell the same.
Probably not. But it would depend if you touch them.
Collegen
That would be highly unusual. It would be an act of insanity.
That would be bacteria.
No.... well yes if that is all you eat.
Yes, but why would anyone buy that.
You would be eating waaaay to much for that to happen.
There are 2 anal sphincter's; if they fail then feces will drip out of the anus.
Preserved animal feces from a long time ago would be a fossil trace. Petrified human feces would be called paleofeces. However, fresh animal feces would not be considered a fossil.
Then a human would arrive at an asteroid.
They will eat human, dog feces etc. but it's not advisable to feed it to them if you will be using the worm tea and castings in vegetable gardens etc. for human feces it would be better to build a biogas digester and use the gas to cook with.