well, there is a Conformance Section which is Section 1.
It is the most important section. So while ever project might handle it differently it can either be conformant or non-conformant.
It is super-important that "type" can be multiple (e.g. BBC will probably have 15 or so to describe an item) -
all things are “multiple” except those marked “functional” in the spec.
That said it unfortunately can't be a Link and Object at the same time.
The spec. says
“Note that the Link and Object types are disjoint from one another. That is, any given Object cannot also be a Link.” https://www.w3.org/TR/activitystreams-core/#link
(last sentence)