With some transitive Esperanto verbs, one can choose between two or more object roles to take the position of the direct object (accusative object). (A Q&A of the Konsultejo mentions demandi and peti.) E.g., with demandi the question can be the direct object:
Sophia demandas tiun demandon al Adamo.
but just as well, the person being asked can be the direct object:
Sofia demandas Adamon pri tio.
The respective other objects are used with prepositions. Because either object can be the direct object (with these verbs — that isn't the case for all transitive verbs), and because there can only be one direct object, there's always a preposition the direct object could get to indicate its role if it weren't the direct object.
With such transitive verbs, is it allowed to use prepositions for all objects (and thus have no direct object), even if one of them could be a direct object? I.e., can the second example from above be rephrased like this?
Sofia demandas al Adamo pri tio.