1) Yes, it is difficult to answer about climate in Russia, because Russian Federation is the largest country in the world, so the weather is rather different in different reegions.
2) As I said before, Russian Federation takes almost a half of the planet, so the climate depends on the region of the country: is it northern or southern, does it stand near to the sea or not.
3) The weather on the south is hot. If a city stands on the river or near to the sea there is no dry winds, the climate is favorable. If city does not stand on the river or near to the sea, there might be an aridity in the city, often fires. In the north, usually the annual average temperature does not reach over 20 degrees.
4) The swimming season usually starts in April and ends in November.
5) In European part of the country sometimes it rains, the weather is cloudy, especially in St. Petersburg, but usually the weather is favorable: hot summer, cold winter.
6) The autumn usually comes earlier in Siberia.
7) In the south part It is usually 0-20 degrees, in north part it is usually -15 - 10 degrees.
8) The winter is a good time for snowboarding, skiing, skating.