Well I want to know.

Does pedophilia have to be exclusive or a primary/preference sexuality to be considered so? What if you are panfluid or whatever in terms of age?
Is there any psychology behind being limitless towards any age (over at least 8 and under 90) but with no preference in sexuality? I want to know

No, it's not wrong at all, if it not be nigh exclusive, one won't get a medical diagnosis of pædophilia.

You can call yourself a pædophile informally, but it doesn't meet the medical criteria.

First sentence on Wikipedia: “Pedophilia (alternatively spelt paedophilia) is a psychiatric disorder in which an adult or older adolescent experiences a primary or exclusive sexual attraction to prepubescent children.”. [emphasis mine]

A nonexclusive one is actually very common which would make most human beings “pædophiles” if that were admitted.