There are different types of alliances - long-term and ad hoc. The fact that they planned to attack each other in the future did not prevent them from forming an alliance against another country in 1939.
Germany and the USSR attacked Poland together, in agreement - this makes them allies at least for the purposes of the war with Poland.
But Germany attacked the USSR practically in the course of the same war. And the Soviet Union did not help Germany to fight with the nations that were at war (namely England and France). Even though, by the time the USSR invaded Poland, the Allies had already declared war on Germany.
So I think to say they were allies is, at the very least, misleading. But it's a purely nominal question.
Hitler's 1934 pact with Poland was a non-aggression pact and nothing more. The Hitler-Stalin Pact (Ribbentrop-Molotov) was a pact on joint aggression against another country and the division of that country's territory.
You're right. Although the German-Soviet pact was initially and primarily also a non-aggression pact that later evolved into something more. In the original pact there was no hint of the invasion of Poland by the USSR, that is something that, due to circumstances, happened later.
no serious person compares the Polish authorities of the 1930s to the Nazis.
I don't. However, I do believe that it had inclinations, at least, greater toward the Axis than toward any other power center. The same as with Romania, Hungary, Bulgaria and/or Yugoslavia (the latter at the beginning of the conflict). Are all these governments comparable to Germany? Of course not, yet they allied with it.
But I don't think we disagree much either.