The wn._queries module is not part of the public API, nor is any other module prefixed with _. This means that the functions are not documented and they may (and do, occasionally) change from one version to the next without a CHANGELOG entry or change to the major version number. I do not recommend using those.

There is the Synset.get_related() method for finding relations with any available relation name. Similarly for senses is Sense.get_related(), and for sense-to-synset relations there is Sense.get_related_synsets(). Since the last release, both Synset and Sense also have a relations() method which does the same thing but returns a dictionary mapping the relation names to the lists of relations, but unfortunately I forgot to document these. They will be in the next release. The Synset.relation_paths() and Sense.relation_paths() methods return a list of lists of synsets/senses connected by one or more relations.

Methods like Synset.hypernyms() are just for convenience and they capture multiple individual relations. For instance, hypernyms() includes both the hypernym and instance_hypernym relations:

Also, as a general note, it is not the case that all relations in wn.constants.SYNSET_RELATIONS are in use by any one wordnet. A subset of those are used by the English wordnets, another subset by the Polish wordnet, etc.