Can give some light on T-72B with K5 designation if that is not BM..
It's simple.
T-72B (Object 184) can be seen with or without 4S20 Kontakt-1 ERA, there is also T-72B1 (Object 184-1) variant, as T-72B can have or not Kontakt-1, and use simplified FCS without 9K120 Svir system for 9M119 Refleks GLATGM's.
T-72B tanks manufactured somewhere between 1988 to 1989 recived 4S22 Kontakt-5 ERA. These tanks are called by Russians T-72B obr.1989g. These ones were often called T-72B(M) or T-72BM but it is not proper designation for them. There is also slightly newer variant T-72B obr.1990g with slightly improved tank commander cupola.
T-72BU (Object 188) was initial military designation codename for first T-90 (Object 188) variant with cast turret. In fact T-72BU/T-90 (Object 188) is just T-72B "on steroids".
Some T-72B tanks are upgrade to T-72BA standard, this is more a repair program than real modernization, but some of them recive new sights, FCS components etc. Some of them have Kontakt-1 ERA, some have Kontakt-5 ERA.
Newest and most advanced variant was developed during the "Rogatka" program, these tanks are not fielded (yet) as far as I know, and have two military designation codes, T-72BM or T-72B2 and manufacturer designation code Object 184M.
This is how T-72B and T-72B1 looks without and with Kontakt-1 ERA.
This is how T-72B obr.1989g, obr.1990g and T-72BA can look like, with Kontakt-5 ERA.
This is how T-72B2/T-72BM looks like, with Relikt ERA.