And one more thing I have not noticed earlier.
This piece obviously uses P-21/22/27 missile system, so the concern about upgrading with AD is valid IMO.
This is how 3M82 version looks like.
But there is a catch.
When we are talking SSN-2 Styx, we should be aware of the fact, that the name is misleading.
The very same tubes can host P-15, P-15M, P-21. P-22 or P-27 missiles. You can't distinguish.
From P-15M, the missile has increased range, a flight path lowered to 25m, and you can have it with either IR or AR seeker. Till today, the missile is being in production in China as a Silkworm. The missile has a very potent warhead and can be effectively used against any transport vessel, land target, or any less potent naval threat.
I will surprise you, but a long time ago, when PN introduced the very first OHP frigate, they checked the new skills and potential and figured out that ... no PN ship can fight P-21 another way than AK630 at the final approach. SM1 turned to be just the same useless.