The starting point of what? Certainly not the internal instability of Russia. I hope nobody believes you can have a revolution without lots of internal strife preceding it. If you want a starting point for those troubles, you should probably take the shots in Sarajevo in 1914, and the world war that followed.

Look, it was a mess. At that point, Russia was still a feudal state.

And some say that Lenin was actually a German agent, directed to destabilize Russia, and keep it out of WWI.

Russia would have fallen over from the stress of the war regardless, but the Germans did help with the transport of Lenin and some friends. Interestingly, wikipedia also mentions some american investment bankers wanting greater market access (https://en.wikipedia.org/wiki/October_Revolution#American_su...).

That was the reason why the Germans agreed to allow him passage through Germany in the famous "sealed train", yes.