2) Hydrodynamics polymers delivering systems (to greatly enhances ,momentarily, submarine outer hull's hydrodynamics coefficient so to avoid enemy torpedo eventually not seduced/outranged)
Those polymers system were known to be in development and Norman Polmar has hinted at it in this book but these systems were never operationalised on any submarine most certainly on Schuka/Akula class for sure.
I should add here though Soviet/Russian submarine has many qualities that were non appreciated by Western Defence Journal types but professional in US who were not biased did appreciate qualities that russian submarine had lik greater depth , speed , energy , non-acoustic sensors.
Most if the weakness in these areas where over come by west with Sea Wolf and Virginia class submarine which had similar depth , greater speed and other qualities that Soviet submarine enjoyed.
Acoustically Speaking Akula class were equal or even superior to LA class and other western SSN but Sea Wolf and Virginia were acoustically far superior specially at high speed.
Russia would come on par with most modern US submarine with Yasen class and perhaps Yasen-M might even give it some advantage acoustically speaking against most modern Western SSN.
Ofcourse if the entire Zircon-S and 5th gen torpedo program is sucessful then 885M will be a different beast.