Hi Anirudh,
You are right and have cross checked, TN always skipped Kazipet, TN in 1987-1988 time frame used to have electric locos till BZA and from there diesel loco till NGP. GT started skipping KZJ from April 1987 with a stop at Warangal. If understand correctly Kazipet bypass came in early 1975. Not sure whether Cochin JJ or TN was the first train to run thru bypass.