Finally booked retiring room. Booked a ticket in mahalaxmi exp from Satara to CST date 13/02/2018. Code is still CSTM for journeys commencing on or before 13/2/2018. Code changed to CSMT for journeys commencing on 14/02/2018 and after. With the help of STR - CSTM ticket, booked RR from 14-16 feb.