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Haven't put the timeline next to it, but at some point they had sudden access (don't remember from the top of my head when) to Western propellor technology, allowing them to build more bladed skew props rather than their regular rudimentary 5-blade (this event is also referred to as a Japanese scandal, but as far as I know, several European companies were also involved in it).
That was the famous 1987 Toshiba case, in which computer controlled milling equipment was shipped to the then USSR. A Norwegian firm, Kongsberg, was also involved. The CNC machinery allowed the USSR to make the complex shaped skewed propellers that greatly reduced a low frequency noise known as "blade rate". This is caused by the interaction of the standard propeller with the wake of the control surfaces (sternplanes & rudders) forward of the propeller. Skewed blades enter and exit the wake much more gradually, and have other features to reduce the vibration. Blade rate noise carries extremely well with little distortion in the deep sound channel for a long distance.
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And indeed all Russian SSBNs were capable of launching from the surface, the missiles they launched were quite different though. In addition to different length, they 'd also exert a different amount of force to the hull. I guess the Delta IV was just a little too restricted in size to handle the missiles she had.
The Russian missiles are (with one exception) all liquid fueled rockets (usually UDMH and nitrogen teroxide) vs. Western solid fuel rockets. They are also ignited in the launch tubes, rather than being ejected by steam as in the West, with ignition after they enter the air. One Western SSBN, Henry Clay (SSBN 625) did make a surface shot back in the 1960's, but virtually all Western SSBN shots are submerged. The one surface shot was made with the SSBN healed over so that if the missile did not ignite, it would not land back on the submarine (which would make for a real bad day...).