Hello and

Interesting topic
That's a good question. Let's take the dictionary definition:
# the state of being without a flaw or defect
# paragon: an ideal instance; a perfect embodiment of a concept
# the act of making something perfect
source
So 3 seperate definitions really. Let's go with the state of being without a flaw or defect. Problem arises; what constitutes as a flaw or defect? A siamise twin perhaps? But surely that is only a flaw in the sense that it is against the norm? In which case, perfection as a state of being is completely dependant upon society's perception.
Can something perfect create imprefection?
All a matter of intention and context; for example a supplier of ketchup may dilute his product with water so he may stretch his product and essentially tripple his sales. Clearly an imperfect product. Admittedly, this is assuming the supplier is perfect which certainly impacts heavily on the example. In which case, it'd be rather difficult to give an appropriate example, unless you were referring to God.
Can pefection be improved on?
Depends on the actual definition. Though i'll attempt an answer in a general sense of perfection: person A scores 98 out of 100 in his test. He cannot be called perfect (in relation to the test) because he clearly made a flaw (and lost 2 marks). But, person A is perfect compared to those who scored 0. (Though, maybe that's just a matter of perception?)
Can something perfect make mistakes?
Matter of intent. Also, have to clarify what constitutes as a mistake (i.e is it really a mistake or is it a matter of perception)
Can you add or subtract from something perfect and make it better?
Depends on how broad the definition of perfection is. Though, one answer that is feasable is a simple No.
Depends on your perception and definition of perfection. I personally believe the shark is the perfect predator (seeing as it hasn't had to evolve, plus it's a pure killing machine!) but one could easily dispute that with the fact that the shark isn't truly perfect, since it's only good at being a predator (one class, for example). In other words, it depends on how broad a definition you give to perfection; is it something individual or is it a general thing.
So it really depends on what perfection means.