A place for students, teachers and native Russian speakers to discuss Russian grammar, vocabulary, pronunciation, and other aspects of the Russian language.
How does one know if one of the many exceptions to a spelling or grammar rule is valid or used properly?? It may just be made up by the speaker or writer or obsolete. Is there a Russian language authority to review such matters?
You can find useful this link. It provides all possible forms of really many Russian words.
There is no authority to dictate to the language, only to describe it while trying to be at the edge.