These questions cover a lot of ground.
Germany prior to its imperial unification about 1875 was a collection of various duchies, principalities, archbishoprics, kingdoms, and independent cities. Each one of these regions had a long history and a great deal of pride; frequently also they were divided by religious lines (Lutheran vs. Catholic after the Reformation) and by Imperial privileges.
The Congress of Vienna met after the final defeat of Napooleon in 1815. The major powers agreed to respect each other's borders and also agreed to assist each other in suppressing revolutionary movements. There were widespread revolts in Europe in 1848 (brought about in many locations by famine conditions), but except for France they were all suppressed. However Germany established a customs union about 1830 or so and various states agreed to finance joint railway projects.
As for Russia, Prussia and Russia were allies against France for quite some time. The diplomatic revolution occurred about 1900 when France and Russia drew closer together in mutual fear of Germany (which was expansionist and which was engaged in a massive military build up).