"Do not cook it"

[aboutpurpo]

The infix might change depending on what the object was, right? For example if we were taking about an onion, it would read "usikipike."

[likes2hike]

Correct! All variants should be accepted. :)

[Mightyone]

Is this a negative imperative? So in this case we have both subject and object infixes?

[rokksolidrees]

Yes, u- is the subject prefix and -si- is the negative and -i- is the object infix.