2) It makes sense to launch from an as southern point as you can because Earth rotation boosts you more and you need less fuel. Ideally, it should be the equator, but due to political reasons it's difficult. The French went this way, and they now have to use the French Foreign Legion for protection there.

In the Soviet Union, Baikonur was pretty much as south as you can go, especially given that you want to launch from a place where your rockets have space to crash without killing too many people and you also want to avoid the scenario where some foreign dudes overrun your spaceport (the most southern point of the Soviet Union was on the Afghan border).

After the breakup of the Soviet Union it made sense to lease this spaceport from Kazakhstan. It's currently leased until 2050, however Russia has two other active spaceports, Plesetsk and Kapustin Yar, the former is being up north and mostly used for special military stuff (northern launch sites are useful for some fancy orbits), and the latter is predictably south. Svobodny was a backup spaceport built on the southern border with China in case Kazakhstan goes rogue and cancels the lease, but it's not used now because Kazakhstan is a glorious republic. Vostochny in the same area will be finished by the end of this year and will be used instead of Baikonur then.