There is often debate about the 'unitariness' or otherwise of some of these structures. In
The aeroplane took off.
He took off (= impersonated) Groucho Marx. ,
there is little argument over the fact that 'take off' is behaving as a single verb. Though some people prefer not to use the term 'multi-word verb' here.
He took off his coat / He took his coat off, there seems more of an argument for verb and adverb (or intransitive preposition) - two components rather than one.
He looked up the answer.
He looked up the hill.
Now, I'd say that with:
I carefully pried open her mouth. / I carefully pried her mouth open. ,
we're somewhere in the grey area
pry open = MWV?
pry = verb; open = adverb?
Certainly, the pretty comprehensive 'Oxford Dictionary of Phrasal Verbs' doesn't include pry open.
In the structure shown by
He went unarmed. ,
unarmed is a predicative adjective, coming after the linking verb.
in the similar structure shown by
He hammered the metal flat. ,
hammer is a transitive verb still able to fulfil a linking role. This type of structure is often described as secondary predication though Cobuild just labels the adjective (flat here) an object complement.
In she left the door open, open is indisputably an adjective.
In she forced the door open, I think most people would again accept open as an adjective.
In she pried open the door, I think it's sensible to accept the same analysis.