All 3 acronyms originally referred to the "Karlovsky synod" which was the part of the Russian Church that went into exile when the Bolsheviks took over the Russian Church inside Russia. This was the case up until about the year 2000.
Today there are a number of schisms all calling themselves ROCOR. Also, the ROCOR-MP calls itself ROCOR. Fr. Seraphim predicted this would happen. To be sure of any group calling itself ROCOR, you have to find out who is the bishop.
ROCOR under Metropolitan Agafangel (Pashkovsky) is the only valid continuation of the ROCOR.
ROCOR Parishes under Metropolitan Agafangel are listed here: