HELP: adpositions

Hello,

I came in late.

What is a "true" adposition?

Is a gentive particle a true adposition?

Could a particle that conveys apposition be a true preposition?

In creating some postpositions for my upcoming language, Kranuwe, I have
found that some of my proposed postpositions can only form noun-modifying
PP's, and some can only form verb-modifying PP's, and some can form PP's
that modify both nouns and verbs.  Can I accurately call them all
postpositions?

Thanks to all who answer this question,

All the best to everybody,

Jim