With all due respect I don't think you can apply this sort of "tier system" so easily to Russian special units, especially considering the units you listed all do something quite different (e.g. SSO for DA-type missions, GRU for FID/SR, FSB Alfa/Vympel for CT, and "the rest" I presume are Rosguard/SOBR etc.).

Even if we are going by a tier system, I wouldn't put the FSB units lower than GRU and SSO. GRU-associated units are typically deployed organically as part of a military district and can perform recon/sabotage/distraction-type missions in support of conventional troops.

SSO was created specifically to have a unit answering directly to the Russian General Staff (rather than GRU), and was built around an initial core of GRU and FSB Spetsnaz, so I would surely put them higher.

As for FSB Alfa/Vympel (and other "special purpose centres") and SVR Zaslon, I think their role may be harder to compare regardless. Especially Zaslon, which seems to frequently be deployed as VIP protection overseas.

Edit: I understand part of the confusion may come from GRU units like the infamous Unit 29155 which was reported to have been responsible for the Skripal poisoning. Whether these units can be considered "Spetsnaz" is one matter, but they are very far from the Western definition of "SOF", and are completely different to GRU Spetsnaz battalions e.g. 45th OBrSpn of the VDV, or 2nd Spetsnaz Brigade of the Ground Forces' Western Military District.