Don't feel bad asking the question. And just because people here have strong opinions, does not mean an issue is absolutely settled.
Stalin was a cautious but opportunistic person. The Soviets wanted the land lost in WW1 back, but Lenin/Stalin had not launched an offensive war between 1922 and 1939. I doubt Stalin, himself, could tell you under what exact conditions he would attack the Germans, but he would not have passed up an opportunity at a weak target. Stalin also apparently trusted Hitler for some reason, so it is even possible Stalin would honor the non-aggression pact for the 10 years. I have seen lots of strong opinion on what Stalin would have done, but I have never seen good primary source material. (i.e. Soviet GHQ meetings discussing the attack criteria, Stalin's secret Journal, etc.) Stalin was reorganizing his army in 1941, and important equipment was coming on line in mid-1942, so earlier than 1943 is unlikely, unless it looks like Hitler is losing badly.
Now to Nazi perspective. The have to decide to delay the expansion to the east, live with exposed oil facilities in Romania and live with the Risk of the Soviet surprise attack. The Nazi have to leave large defensive armies in the east to keep Stalin honest. They may need to accept Stalin moving into Turkey. But ok, the Nazi's decide it is the best way forward. What can they do?
1) They lack a navy, and it will take a half decade to build a real surface fleet, if not longer. Invading Britain will not work.
2) Trying the air attacks on England makes sense, since it has not been tried before to that scale. It does not work, cancelled after a few months.
3) Focus on U-boats and air power to try to starve the UK. This plan may work, but it will likely take years.
4) Neutralize/Take Malta. Malta can be neutralized by air power to a large extent. When it was German, not Italian air planes responsible for Malta, the UK had a very hard time. Taking it will be difficult, but even just neutralizing it helps a lot with supply in Africa.
5) Gibraltar - Either this or the Suez needs to be shut down to make the Med an Axis lake. The Suez is not practical unless Malta is taken, which is hard, but not impossible. So the Axis need Spain to join, badly. Franco did/will demand a lot. But Gibraltar is conquerable, and even in a worst case that it is not conquerable, the straights can be closed through mines, air power, and light naval assets to at least freighters. Running a freighter through the straights at 15 knots speed, when the air patrols will spot the convoy 100's of miles out is not possible.
6) Suez - After dealing with Malta and maybe Gibraltar, the Germans have more than enough troops to take the Suez, but logistics still will be hard as long as the British have a Navy in Egypt. It is not clear to me who would win assuming both Malta and Gibraltar are neutralized/captured.
Ok, lets assume a near best case for the Axis in November 1941. Stalin is honoring the pact and has he troops in a defenses in depth deployment. The submarine warfare is going well, better than OTL due to air power in Spain and much greater resources to the U-boat command. Gibraltar is captured. Malta has been captured. The supply situation was much better, and Rommel has 2 to 3 times more forces and has captured the Suez. Half of the German army remains in defensive positions near the Soviet Union to Stalin honest. The Axis is in much better shape, but it is not a clear winner. Japan will still do Indochina and Pearl Harbor. The USA will go on full war fitting, and FDR will find a way to get his troops to Europe, but it might take bit longer. Germany has still has no way to drive England from the war, and the USA/UK will have a hard time with the German land forces. At this point in time, does it make sense for Germany to try to conquer Africa or drive for India. The logistics are horrible. Now with 200+ division available for the Western Front, D-Day would be very hard. (Look at Calbear AA timeline for an idea of how hard.)
Now German is much better off and has a chance to win in this ATL, but it is not certain. The war will last longer than OTL, because the USA will need to train a lot more divisions than OTL, and the great losses on the Eastern Front will be USA/UK troops, not USSR. Not at the same ratio, but millions of American soldier will die, because at the end of the day, to kill a German infantry regiment requires an equal or larger size unit to engage in close combat.
Stalin will likely wait until it is clear the UK/USA have broken the back of the German military, then join in at the end for an easy gain, much like he did in Manchuria. The USA/UK looking at millions of dead, will give Stalin what he wants to join. Stalin non-aggression pact was a good idea for Stalin, if one assumes Hitler would honor it.